U.S. patent application number 12/829164 was filed with the patent office on 2010-10-21 for resin composition for optical material, resin film for optical material and optical waveguide using same.
Invention is credited to Tatsuya Makino, Masami Ochiai, Tomoaki Shibata, Atsushi Takahashi, Toshihiko Takasaki.
Application Number | 20100266258 12/829164 |
Document ID | / |
Family ID | 36142761 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100266258 |
Kind Code |
A1 |
Shibata; Tomoaki ; et
al. |
October 21, 2010 |
RESIN COMPOSITION FOR OPTICAL MATERIAL, RESIN FILM FOR OPTICAL
MATERIAL AND OPTICAL WAVEGUIDE USING SAME
Abstract
Disclosed is a resin composition for an optical material which
contains a base polymer (A), a photopolymerizable compound (B), and
a photopolymerization initiator (C). Also disclosed is a resin film
for an optical material which is made of such a resin composition
for an optical material. Specifically disclosed is a resin
composition for an optical material which has high transparency and
high heat resistance, while enabling formation of a thick film with
high precision. This resin composition is particularly useful for a
resin film which is used for forming optical waveguides. Also
specifically disclosed are a resin film for an optical material
using such a resin composition and an optical waveguide using such
a resin film.
Inventors: |
Shibata; Tomoaki; (Ibaraki,
JP) ; Makino; Tatsuya; (Ibaraki, JP) ; Ochiai;
Masami; (Ibaraki, JP) ; Takahashi; Atsushi;
(Ibaraki, JP) ; Takasaki; Toshihiko; (Ibaraki,
JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
36142761 |
Appl. No.: |
12/829164 |
Filed: |
July 1, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11576834 |
Feb 5, 2008 |
7751678 |
|
|
PCT/JP05/18635 |
Oct 7, 2005 |
|
|
|
12829164 |
|
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|
Current U.S.
Class: |
385/141 ;
430/321 |
Current CPC
Class: |
C08L 33/068 20130101;
C08L 63/10 20130101; G03F 7/032 20130101; C08F 2/50 20130101; C08L
33/062 20130101; G02B 6/138 20130101; C08L 71/12 20130101; C08L
63/10 20130101; C08L 33/062 20130101; G03F 7/027 20130101; C08L
33/068 20130101; C08L 2666/22 20130101; C08L 2666/02 20130101; C08L
2666/22 20130101 |
Class at
Publication: |
385/141 ;
430/321 |
International
Class: |
G02B 6/00 20060101
G02B006/00; G03F 7/20 20060101 G03F007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 10, 2004 |
JP |
2004-294703 |
Dec 13, 2004 |
JP |
2004-359796 |
Dec 13, 2004 |
JP |
2004-359797 |
Mar 15, 2005 |
JP |
2005-073809 |
May 11, 2005 |
JP |
2005-138406 |
Aug 24, 2005 |
JP |
2005-243430 |
Aug 24, 2005 |
JP |
2005-243431 |
Aug 24, 2005 |
JP |
2005-243432 |
Aug 24, 2005 |
JP |
2005-243433 |
Claims
1. A flexible optical waveguide, comprising one resin film for
forming a core layer and two resin films for forming a cladding
layer, wherein at least one of the resin films for forming a
cladding layer is composed of a resin for forming a cladding layer
and a base material film, and the base material film is arranged on
an outer side of the cladding layer with respect to the core
layer.
2. A flexible optical waveguide according to claim 1, wherein each
of the resin films for forming a cladding layer comprises a base
material film subjected to adhesion treatment and a film of the
resin for forming a cladding layer formed on the base material
film.
3. A method of fabricating a flexible optical waveguide,
comprising: curing a resin film for forming a cladding layer
composed of a resin for forming a cladding layer and a base
material film, to form a cladding layer; laminating a resin film
for forming a core layer on the cladding layer, to laminate a core
layer; exposing the core layer to light and developing the core
layer to form a core pattern of an optical waveguide; and
laminating a resin film for forming a cladding layer on the core
pattern and curing the resin for forming a cladding layer.
4. A method of fabricating a flexible optical waveguide according
to claim 3, wherein the resin film for forming a cladding layer
comprises the base material film, subjected to adhesion treatment,
and a film of the resin for forming a cladding layer, formed on the
base material film.
Description
[0001] This application is a Divisional application of application
Ser. No. 11/576,834, filed Feb. 5, 2008, which is a National Stage
application, filed under 35 USC 371, of International (PCT)
Application No. PCT/JP2005/018635, filed Oct. 7, 2005. The contents
of Ser. No. 11/576,834, filed Feb. 5, 2008, are incorporated herein
by reference in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to a resin composition for an
optical material having excellent heat resistance, transparency,
and productivity, a resin film for an optical material, and an
optical waveguide using the film as well as to a flexible optical
waveguide having excellent flexibility, toughness, and productivity
and to a method of producing the same.
BACKGROUND ART
[0003] To cope with an increase in volume of information
concomitant with popularization of the Internet and Local Area
Network (LAN), optical interconnection technology that uses optical
signals is being under development not only in communication fields
of main line and access type but also in short distance signal
transmission between boards or in boards of routers and server
devices. Specifically, to enable use of light in short distance
signal transmission between boards or in boards in routers and
server devices, optical/electronic boards that include an electric
printed wiring board and an optical transmission path are under
development.
[0004] In this case, it is desirable to use as the optical
transmission path an optical waveguide that has a higher degree of
freedom in wiring and is capable of being provided in higher
density than optical fibers. Among others, optical waveguides made
of polymer materials, which are excellent in processability and
cost performance, show promise. Polymer optical waveguides have a
structure that is adapted to coexist with electric printed wiring
boards as mentioned above, they are required to have high heat
resistance in addition to high transparency (low transmission
loss). As materials for such an optical waveguide, fluorinated
polyimides (see, for example, Patent Document 1 and Non-patent
Document 1), deuterized silicone resins (see, for example,
Non-patent Document 2), and epoxy resins (see, for example, Patent
Document 2 and Non-patent Document 3) have been proposed.
[0005] On the other hand, the optical waveguides for use in the
above-mentioned utility are required to have a core size of
generally 50 .mu.m square to ensure tolerance of connection with a
light receiving or emitting device. This means that the core layer
must have a thickness of about 50 .mu.m. However, when materials
for waveguides including, for example, deuterized silicone resins
or fluorinated polyimides are used, there arises a problem in that
it is difficult to realize a thickness of about 50 .mu.m on an
optical/electronic board or, if it is possible to realize,
precision of film thickness will be poor because the materials for
waveguides are generally include solvents having low viscosities
although the resins themselves have high heat resistance to endure
about 300.degree. C.
[0006] Further, when fluorinated polyimide waveguide materials,
which themselves have high heat resistance to endure about
300.degree. C. and high transparency as high as 0.3 dB/cm at a
wavelength of 850 nm, are used, film formation on an electric
printed wiring board was difficult to be performed since film
formation requires heating at 300.degree. C. or more for several
tens minutes to several hours. Further, fluorinated polyimides have
no photosensitivity, so the method of fabricating optical
waveguides by exposure to light and development can not be applied
thereto, and they thus have poor productivity and poor
applicability to large-area fabrication. Further, since optical
waveguides are fabricated by a film forming method that involves
applying a liquid material on a substrate, management of film
thickness is cumbersome and in addition, the resin applied on the
substrate is still liquid before curing, so the resin will flow on
the substrate to make it difficult to maintain uniformity of film
thickness. Thus, there are many problems arising from the fact that
the form of the material is liquid.
[0007] Further, the upper cladding after the core has been embedded
must have flatness taking into consideration of subsequent mounting
of light receiving or emitting devices. However, when liquid
waveguide materials are used for the upper cladding, there tends to
occur unevenness as a result of following up the ridge pattern of
the core, so it is difficult to realize flatness.
[0008] The epoxy resins have problems similar to those of the
above-mentioned waveguide materials including deuterized silicone
resins or fluorinated polyimides because the epoxy resins are
liquid.
[0009] That is, heretofore, epoxy resins for forming optical
waveguides are those epoxy resins that are liquid at room
temperature, or solid epoxy resins diluted with solvents have been
used. These epoxy resins have excellent transparency and heat
resistance at about 200 to 280.degree. C. However, since an epoxy
resin is used for fabricating optical waveguides by applying a
liquid material on a substrate and forming a film by, for example,
a spin coating method, management of film thickness is cumbersome
and in addition, the resin applied on the substrate is still liquid
before curing, so the resin will flow on the substrate to make it
difficult to maintain uniformity of film thickness. Thus, there are
many problems arising from the fact that the form of the material
is liquid.
[0010] Further, the epoxy resin is capable of forming core patterns
by an exposure to light and development method by addition of an
optical polymerization initiator and is reported to have a high
transparency of 0.1 dB/cm. However, the epoxy resins generally have
heat resistance of 200 to 280.degree. C. and to obtain high
reliability, they are required to have still higher heat resistance
although some of them are applicable to the above-mentioned
optical/electronic board.
[0011] As mentioned above, none of the conventional resins for
forming optical waveguides has in combination (1) high
transparency, (2) high heat resistance, (3) high-precision film
formability, and (4) acceptable productivity.
[0012] Further, in high speed, high-density signal transmission,
between electronic devices or printed wiring boards, transmission
through the conventional electric wiring is approaching to a limit
of attaining high speed and high density due to restrictions of
mutual interference and attenuation of signals. To break through
such restrictions, the technology of connecting electronic devices
and printed wiring boards to each other by means of light,
so-called optical interconnection is being studied. As the light
path, flexible optical waveguides having flexibility are considered
to be suitable from the viewpoints of ease of connection to devices
and substrates and ease of handling.
[0013] Flexible optical waveguides include polymer film optical
waveguides described in, for example, Patent Document 3. Polymer
films are formed as follows. A solution of a polymer or the like is
applied on a substrate such as silicon by spin coating and is baked
to form a lower cladding layer. In the same manner, a core layer is
formed and then a mask pattern is formed with, for example, a
Si-containing photoresist and dry-etched to form a core pattern.
After that, an upper cladding layer is formed in the same manner as
that in which the lower cladding layer is formed. Finally, the
resultant optical waveguide is peeled from the substrate to
fabricate a film-made optical waveguide. In particular, to make it
easy to peel the optical waveguide, there is shown a method in
which a thermally oxidized silicon substrate is used as the
substrate and after the formation of the optical waveguide, the
substrate having the optical waveguide thereon is immersed in
hydrofluoric acid to separate the optical waveguide.
[0014] However, in the case of the above-mentioned film optical
waveguide, each of the lower cladding, core, and upper cladding
layers is formed by spin coating and baking. This method takes much
time for forming each layer and in addition has problems arising
from the fact that the form of the material is liquid. That is,
since optical waveguides are fabricated by a film forming method
that involves applying a liquid material on a substrate, management
of film thickness is cumbersome and in addition, the resin applied
on the substrate is still liquid before curing, so the resin will
flow on the substrate to make it difficult to maintain uniformity
of film thickness. Also, the method is not suitable for mass
production of optical waveguides having a size of 10 cm or more
because of use of silicon for substrates.
[0015] Further, the above-mentioned production method involves a
step of dry etching, which is a high vacuum process, so dry etching
must be performed for a very long period of time to fabricate
multi-mode optical waveguides having a thick core layer.
[0016] Patent Document 1: Japanese Patent No. 3085666
[0017] Patent Document 2: Japanese Patent Application Laid-Open No.
6-228274
[0018] Patent Document 3: Japanese Patent Application Laid-Open No.
7-239422
[0019] Non-patent Document 1: Journal of Japan Institute of
Electronics Packaging, Vol. 7, No. 3, pp. 213-218, 2004
[0020] Non-patent Document 2: IEEE Journal of Lightwave Technology,
Vol. 16, pp. 1049-1055, 1998
[0021] Non-patent Document 3: Optics ("Kogaku"), vol. 3, No. 2, pp.
81-83, 2002
DISCLOSURE OF THE INVENTION
[0022] In view of the above-mentioned problems, it is an object of
the present invention to provide a resin composition for an optical
material that allows formation of a thick film having high
transparency, high heat resistance, and high precision and has high
productivity and that is particularly useful for resin films for
forming optical waveguides, a resin film for an optical material
using such a resin composition, and an optical waveguide using such
a film. It is another object of the present invention to provide a
flexible optical waveguide having high flexibility and toughness
and in addition having excellent productivity and a method of
producing the same.
[0023] The inventors of the present invention have made extensive
studies and as a result, they have found that the above-mentioned
objects can be achieved by using specified photopolymerizable
compounds and by using a resin composition containing a base
polymer, a photopolymerizable compound, and a polymerization
initiator.
[0024] That is, the present invention relates to the following.
[0025] (1) A resin composition for an optical material,
including:
[0026] (A) a base polymer;
[0027] (B) a photopolymerizable compound; and
[0028] (C) a photopolymerization initiator.
[0029] (2) A resin composition for an optical material,
including:
[0030] (B) a photopolymerizable compound that is fluorene
di(meth)acrylate represented by the following general formula (I);
and
[0031] (C) a photopolymerization initiator,
##STR00001##
wherein X is represented by the following formula (II); Y is
hydrogen or a methyl group; and m and n are each an integer of 1 to
20;
##STR00002##
wherein R1 to R16 independently represent hydrogen, an alkyl group
having 1 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon
atoms, an alkoxycarbonyl group having 2 to 7 total carbon atoms, an
aryl group having 6 to 10 carbon atoms, or an aralkyl group having
7 to 9 carbon atoms.
[0032] (3) A resin composition for an optical material according to
Item (1), in which the photopolymerizable compound (B) has an
ethylenically unsaturated group in a molecule thereof.
[0033] (4) A resin composition for an optical material according to
Item (3), in which the photopolymerizable compound (B) is
epoxy(meth)acrylate or acryl (meth)acrylate.
[0034] (5) A resin composition for an optical material according to
Item (3), in which the component (B) contains fluorene
di(meth)acrylate represented by the following general formula
(I):
##STR00003##
wherein X is represented by the following formula (II); Y is
hydrogen or a methyl group; and m and n are each an integer of 1 to
20;
##STR00004##
wherein R1 to R16 independently represent hydrogen, an alkyl group
having 1 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon
atoms, an alkoxycarbonyl group having 2 to 7 carbon atoms, an aryl
group having 6 to 10 carbon atoms, or an aralkyl group having 7 to
9 carbon atoms.
[0035] (6) A resin composition for an optical material according to
Item (3), wherein the component (B) contains (meth)acrylate
represented by the following general formula (III):
##STR00005##
wherein R.sup.17 is --CH.sub.2CH(OH)CH.sub.2--,
--(C.sub.2H.sub.4O).sub.hC.sub.2H.sub.4--,
--(C.sub.3H.sub.6O).sub.iC.sub.3H.sub.6--, or
--(C.sub.2H.sub.4O).sub.j--(C.sub.3H.sub.6O).sub.kC.sub.3H.sub.6--;
U is --C(CH.sub.3).sub.2--, --CH.sub.2--, --SO.sub.2--, or --O--; V
is hydrogen or halogen; and W is hydrogen or --CH.sub.3, provided
that h, i, j, and k are each an integer of 0 to 10.
[0036] (7) A resin composition for an optical material according to
Item (1), wherein the resin composition contains as the component
(B) a compound having 2 or more epoxy groups in a molecule
thereof.
[0037] (8) A resin composition for an optical material according to
any one of Items (1) and (3) to (7), wherein the base polymer (A)
has a number average molecular weight of 5,000 or more.
[0038] (9) A resin composition for an optical material according to
any one of Items (1) and (3) to (8), wherein the base polymer (A)
has an aromatic skeleton in a main chain thereof.
[0039] (10) A resin composition for an optical material according
to Item (9), wherein the base polymer (A) includes as structural
units of the copolymer components:
[0040] (a-1) at least one member selected from the group consisting
of bisphenol A, a bisphenol A type epoxy compound, and derivatives
thereof; and
[0041] (a-2) at least one member selected from the group consisting
of bisphenol F, a bisphenol F type epoxy compound, and derivatives
thereof.
[0042] (11) A resin composition for an optical material according
to Item (9), wherein the base polymer (A) includes a phenoxy
resin.
[0043] (12) A resin composition for an optical material according
to any one of Items (1) and (3) to (8), wherein the base polymer
(A) includes an epoxy resin that is solid at room temperature.
[0044] (13) A resin composition for an optical material according
to any one of Items (1) and (3) to (12), wherein:
[0045] the content of the component (A) is 5 to 80 mass % and the
content of the component (B) is 20 to 95 mass % with respect to a
total content of the components (A) and (B); and
[0046] the content of the component (C) is 0.1 to 10 mass parts
with respect to 100 mass parts of the components (A) and (B) in
total.
[0047] (14) A resin composition for an optical material according
to Item (13), wherein the content of the component (A) is 10 to 80
mass % and the content of the component (B) is 20 to 90 mass % with
respect to a total content of the components (A) and (B).
[0048] (15) A resin composition for an optical material according
to any one of Items (1) to (14), wherein the content of the
component (B) is 90 to 99.9 mass % and the content of the component
(C) is 0.1 to 10 mass % with respect to a total mass of the
components (B) and (C).
[0049] (16) A resin film for an optical material, including the
resin composition according to any one of Items (1) and (3) to
(15).
[0050] (17) A resin film for an optical material according to Item
(16), wherein the resin film for an optical material is a resin
film for forming optical waveguides, and a cured product of the
film has an optical transmission loss of 0.5 dB/cm or less.
[0051] (18) An optical waveguide, including the resin film for an
optical material according to Item (17) as at least one of a lower
cladding, a core, and an upper cladding of the optical
waveguide.
[0052] (19) A method of fabricating an optical waveguide,
including:
[0053] a first step of laminating a resin film for an optical
material on a substrate to form a lower cladding layer;
[0054] a second step of laminating a resin film for an optical
material having a refractive index higher than that of the lower
cladding layer on the lower cladding layer to form a core
layer;
[0055] a third step of exposing the core layer to light to develop
the core layer to form a core pattern of an optical waveguide;
and
[0056] a fourth step of laminating a resin film for an optical
material having a refractive index lower than that of the core
layer to form an upper cladding layer,
[0057] wherein at least one of the resin films for optical
materials used in the first step, the second step, and the fourth
step is the resin film for an optical material according to Item
(16) or (17).
[0058] (20) A flexible optical waveguide, including one resin film
for forming a core layer and two resin films for forming a cladding
layer, wherein at least one of the resin films for forming a
cladding layer is composed of a resin for forming a cladding layer
and a base material film, and the base material film is arranged on
an outer side of the cladding layer with respect to the core
layer.
[0059] (21) A flexible optical waveguide according to Item (20),
wherein the resin films for forming a cladding layer each include a
base material film subjected to adhesion treatment and a film of
the resin for forming a cladding layer formed on the base material
film.
[0060] (22) A flexible optical waveguide according to Item (20) or
(21), wherein at least one of the resin film for forming a core
layer and the two resin films for forming a cladding layer is the
resin film for an optical material according to Item (17).
[0061] (23) A method of fabricating a flexible optical waveguide,
including:
[0062] a first step of curing a cladding layer in a resin film for
forming a cladding layer composed of the resin for forming a
cladding layer and a base material film to form a cladding
layer;
[0063] a second step of laminating a resin film for forming a core
layer on the cladding layer to laminate a core layer;
[0064] a third step of exposing the core layer to light to develop
to form a core pattern of an optical waveguide; and
[0065] a fourth step of laminating a resin film for forming a
cladding layer on the core pattern and curing the resin for forming
a cladding layer.
[0066] (24) A method of fabricating a flexible optical waveguide
according to Item (23), wherein the resin film for forming a
cladding layer includes a base material film subjected to adhesion
treatment and a film of the resin for forming a cladding layer
formed on the base material film.
[0067] (25) A method of fabricating an optical waveguide according
to Item (23) or (24), wherein at least one of the resin film for
forming a core layer and the two resin films for forming a cladding
layer is the resin film for an optical material according to Item
(17).
[0068] The resin composition for an optical material of the present
invention has high transparency and high heat resistance. The resin
film for an optical material including the composition has high
transparency and high heat resistance and allows for high-precision
formation of a thick film. Further, use of the resin film for an
optical material enables production of optical waveguides having
excellent performance with high productivity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0069] FIG. 1 is a schematic diagram illustrating the process of
forming an optical waveguide pattern.
[0070] FIG. 2 is a diagram illustrating the method of producing a
flexible optical waveguide.
DESCRIPTION OF SYMBOLS
[0071] 1; lower cladding layer
[0072] 2; substrate
[0073] 3; core layer
[0074] 4; base material (for forming a core layer)
[0075] 5; photo mask
[0076] 6; core pattern
[0077] 7; upper cladding layer
[0078] 8; base material film (for forming a cladding layer)
[0079] 9; lower cladding layer
[0080] 10; core layer
[0081] 11; base material (for forming a core layer)
[0082] 12; photo mask
[0083] 13; core pattern
[0084] 14; upper cladding layer
[0085] 15; base material film (for forming a cladding layer)
BEST MODE FOR CARRYING OUT THE INVENTION
[0086] The resin composition for an optical material of the present
invention is a resin composition that includes (A) a base polymer,
(B) a photopolymerizable compound, and (C) a photopolymerization
initiator. Alternatively, the resin composition for an optical
material of the present invention is a resin composition that
includes a fluorene di(meth)acrylate as the photopolymerizable
compound (B) and the photopolymerization initiator (C).
[0087] The base polymer (A) as used herein is to ensure strength of
a cured product such as a film when such a cured product is formed
and is not particularly limited as far as it can achieve such an
object. Examples of the base polymer (A) include phenoxy resins,
epoxy resins, (meth)acrylic resins, polycarbonate resins,
polyallylate resins, polyether amides, polyether imides, polyether
sulfones, and derivatives thereof. The base polymers may be used
singly or two or more of them may be used as admixtures.
[0088] Among the base polymers exemplified as mentioned above,
those having aromatic skeleton in the main chain are preferable, in
particular, phenoxy resins are preferable, from the viewpoint of
high heat resistance. Further, from the viewpoint of being capable
of being three-dimensionally cross-linked to increase heat
resistance, epoxy resins, in particular, epoxy resins that are
solid at room temperature are preferable.
[0089] Further, when the resin composition of the present invention
is used to form films, it is important to ensure transparency of
the film. For this purpose, the base polymer must have high
compatibility with the photopolymerizable compound (B) described in
detail hereinbelow. From this point of view, the above-mentioned
phenoxy resins and (meth)acrylic resins are preferable. Note that
the (meth)acrylic resin as used herein refers to acrylic resins and
methacrylic resins.
[0090] The phenoxy resin is an amorphous polymer and generally
represented by the following general formula (IV).
##STR00006##
[0091] Here, n is an integer of 1 or more; m is 0 or 1; and
--R.sub.0-- is a group represented by the following general formula
(V), (VI), or (VII), or --O--.
##STR00007##
[0092] Here, R.sub.1 to R.sub.10 are independently H, or an organic
group represented by CH.sub.3, CF.sub.3, or the like.
[0093] Among the above-mentioned phenoxy resins, a straight chain
polymer of a bisphenol A type epoxy resin having a repeating unit
represented by the following formula (VIII) has high heat
resistance and hence is preferable.
##STR00008##
[0094] The phenoxy resin of the above-mentioned straight chain
polymer generally is prepared by a one-step method in which
bisphenol A and epichlorohydrin are subjected to polycondensation
reaction or a two-step method in which a low molecular epoxy resin
and bisphenol A are subjected to polyaddition reaction. Specific
examples of the phenoxy resin include "YP-50" (trade name)
manufactured by Tohto Kasei Co., Ltd., and those described in
Japanese Patent Application Laid-Open No. 4-120124, Japanese Patent
Application Laid-Open No. 4-122714, and Japanese Patent Application
Laid-Open No. 4-339852.
[0095] Further, in addition to the phenoxy resins represented by
the above-mentioned general formula (IV), polymers obtained by
polyaddition reaction between various bifunctional epoxy resins and
bisphenols, for example, brominated phenoxy resins (Japanese Patent
Application Laid-Open No. 63-191826, JP-B-8-26119), bisphenol
A/bisphenol F copolymer type phenoxy resins (Japanese Patent No.
2917884, Japanese Patent No. 2799401), phosphorus-containing
phenoxy resins (Japanese Patent Application Laid-Open No.
2001-310939), high heat-resistance phenoxy resins having introduced
therein a fluorene skeleton (Japanese Patent Application Laid-Open
No. 11-269264,Japanese Patent Application Laid-Open No. 11-302373),
and so on are known as phenoxy resins.
[0096] The phenoxy resins mentioned below represented by the
above-mentioned bisphenol A/bisphenol F copolymer type phenoxy
resins are suitable as the component (A) of the present invention.
That is, the phenoxy resin contains as structural units of the
copolymer components (a-1) at least one member selected from the
group consisting of bisphenol A, a bisphenol A type epoxy compound,
and derivatives thereof, and (a-2) at least one member selected
from the group consisting of bisphenol F, a bisphenol F type epoxy
compound, and derivatives thereof.
[0097] The resin film for an optical material made of a resin
composition that includes a resin having the components (a-1) and
(a-2) as the copolymerizable components is particularly suitable as
a resin film for forming an optical waveguide. Use of it can
increase interlayer adhesion of a cladding and a core and pattern
formability (thin line or narrow space responsiveness) at the time
of formation of the core pattern of an optical waveguide so that
fine pattern formation having small line and space is possible.
[0098] Suitable examples of the bisphenol A or a bisphenol A type
epoxy compound or derivatives thereof include tetrabromobisphenol A
and a tetrabromobisphenol A type epoxy compound. Further, suitable
examples of the bisphenol F or a bisphenol F type epoxy compound
and derivatives thereof include tetrabromobisphenol F and a
tetrabromobisphenol F type epoxy compound.
[0099] The base polymer (A) of the present invention includes
particularly preferably a bisphenol A/bisphenol F copolymer type
phenoxy resin as mentioned above, which is available, for example,
as "Phenototo YP-70" (trade name) manufactured by Tohto Kasei Co.,
Ltd.
[0100] Then, the epoxy resin that is solid at room temperature
includes bisphenol A type epoxy resins, for example, "Epototo
YD-7020, Epototo YD-7019, Epototo YD-7017" (trade names)
manufactured by Tohto Kasei Co., Ltd. and "Epikote 1010, Epikote
1009, Epikote 1008" (trade names) manufactured by Japan Epoxy
Resins Co., Ltd.
[0101] The molecular weight of the base polymer (A) is preferably
5,000 or more, more preferably 10,000 or more, and particularly
preferably 30,000 or more in terms of number average molecular
weight in order to make it possible to form even a thick film of
about 50 .mu.m as required for optical waveguides for optical
signal transmission between boards or in a board in routers or
server devices. There is no particular upper limit of the molecular
weight but from the viewpoints of compatibility with the
photopolymerizable compound (B) or the exposure to light and
developability, the molecular weight of the base polymer is
preferably 1,000,000 or less, more preferably 500,000 or less, and
particularly preferably 200,000 or less. Note that the number
average molecular weight in the present invention is a value
determined by measurement by gel permeation chromatography (GPC)
and calculation in terms of standard polystyrene.
[0102] The blending amount of the base polymer (A) is preferably 5
to 80 mass % with respect to the total mass of the components (A)
and (B). When the blending amount of the base polymer (A) is 5 mass
% or more, it is easy to form films of the resin composition that
contains the photopolymerizable compound and photopolymerization
initiator. In particular, the blending amount of 10 mass % or more
is preferable since even a thick film having a film thickness of 50
.mu.m or more can be readily prepared upon film formation.
[0103] On the other hand, when the component (A) is in an amount of
80 mass % or less, the pattern formability of the resin composition
increases and photocuring reaction proceeds sufficiently upon
formation of optical waveguides. From these viewpoints, the
blending amount of the base polymer (A) is set to more preferably
20 to 70 mass %.
[0104] Then, the photopolymerizable compound (B) in the present
invention is not particularly limited as far as it can polymerize
by irradiation of light such as ultraviolet ray. However, from the
reactivity with light, it is preferable that the photopolymerizable
compound (B) be a compound that has an ethylenically unsaturated
group in the molecule. Specific examples thereof include
(meth)acrylates, vinylidene halides, vinyl ether, vinylpyridine,
and vinylphenol. Among these, (meth)acrylates are preferable from
the viewpoints of transparency and heat resistance.
[0105] (Meth)acrylates may be any of monofunctional, bifunctional,
and trifunctional ones.
[0106] Note that "(meth)acrylate" as used herein refers to
acrylates and methacrylates.
[0107] Examples of the monofunctional (meth)acrylate include
methoxypolyethylene glycol(meth)acrylate, phenoxypolyethylene
glycol(meth)acrylate, lauryl(meth)acrylate,
isostearyl(meth)acrylate, 2-(meth)acryloyloxyethyl succinate,
paracumylphenoxyethylene glycol(meth)acrylate,
2-tetrahydropyranyl(meth)acrylate, isobornyl(meth)acrylate,
methyl(meth)acrylate, ethyl(meth)acrylate, butyl(meth)acrylate, and
benzyl(meth)acrylate.
[0108] Further, examples of the bifunctional (meth) acrylates
include ethoxylated 2-methyl-1,3-propanediol di(meth)acrylate,
neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,
2-methyl-1,8-octanediol di(meth)acrylate, 1,9-nonanediol
di(meth)acrylate, 1,10-nonanediol di(meth)acrylate, ethoxylated
polypropylene glycol di(meth)acrylate, propoxylated ethoxylated
bisphenol A diacrylate, ethylene glycol di(meth)acrylate,
triethylene glycol di(meth)acrylate, tetraethylene glycol
di(meth)acrylate, polyethylene glycol di(meth)acrylate,
polypropylene glycol di(meth)acrylate, ethoxylated bisphenol A
di(meth)acrylate, tricyclodecane di(meth)acrylate, ethoxylated
cyclohexane dimethanol di(meth)acrylate,
2-hydroxy-1-acryloxy-3-methacryloxypropane,
2-hydroxy-1,3-dimethacryloxypropane,
9,9-bis[4[(2-acryloyloxyethoxy)phenyl]fluorene,
9,9-bis(3-phenyl-4-acryloylpolyoxyethoxy)fluorene, bisphenol A
type, phenol novolak type, cresol novolak type, and glycidyl ether
type epoxy(meth)acrylates.
[0109] Further, examples of the trifunctional or higher functional
(meth)acrylates include ethoxylated isocyanuric acid
tri(meth)acrylate, ethoxylated glycerol tri(meth)acrylate,
trimethylolpropane tri(meth)acrylate, ethoxylated
trimethylolpropane tri(meth)acrylate, pentaerythritol
tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated
pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol
tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate,
caprolactone-modified ditrimethylolpropane tetra(meth)acrylate, and
dipentaerythritol hexa(meth)acrylate. These may be used singly or
two or more of them may be used in combination.
[0110] As the photopolymerizable compound (B), a single compound
may be used alone or two or more compounds may be used in
admixture. When the above-mentioned bifunctional or higher
functional (meth)acrylates are used, the base polymer can be cured
by being entangled in the three-dimensional network structure
resulting by the polymerization, so it is preferable that at least
one bifunctional or higher functional polymerizable compound be
used as the component (B).
[0111] Among the above-mentioned examples of the component (B),
epoxy(meth)acrylate is a compound that is suitable for obtaining
both transparency and heat resistance simultaneously and it is
preferable that this compound be used in the present invention.
Representative examples of epoxy(meth)acrylates include bisphenol A
epoxyacrylate represented by the following formula (IX). Bisphenol
A epoxyacrylate has excellent compatibility with a phenoxy resin
and can realize high transparency, so it is a very preferable
embodiment to use a phenoxy resin as the component (A) and
bisphenol A epoxyacrylate as the component (B).
[0112] Note that bisphenol A epoxyacrylate is commercially
available as EA-1020 (trade name, manufactured by Shin-Nakamura
Chemical Co., Ltd.).
##STR00009##
[0113] Further, from the viewpoint of transparency, it is
preferable to use acryl(meth)acrylate as the component (B). In
particular, when a (meth)acrylic resin as the component (A) is
combined therewith, the effect is markedly high.
Acryl(meth)acrylate is not particularly limited and generally, it
is a product of addition of a monofunctional (meth)acrylate to a
polymer of glycidyl acrylate. Examples of the monofunctional
(meth)acrylate include various ones, and for example, (meth)acrylic
acid and compounds similar to those exemplified above as the
monofunctional (meth)acrylate can be used.
[0114] When optical waveguides are formed using as a resin film for
forming optical waveguides the resin film for an optical material
made of the resin composition for an optical material of the
present invention, a core film having a high refractive index and a
cladding film having a low refractive index are required as
described in detail hereinbelow. When the resin film for an optical
material of the present invention is used as a core film, the
photopolymerizable compound as the component (B) preferably
contains fluorene di(meth)acrylate as a constituent taking into
consideration high refractive index in addition to high
transparency, high heat resistance, compatibility with the
component (A). In particular, it is preferable that the
photopolymerizable compound as the component (B) contain fluorene
di(meth)acrylate represented by the following general formula (I)
as a constituent.
##STR00010##
[0115] Here, X is represented by the following formula (II); Y is
hydrogen or a methyl group; and m and n are each an integer of 1 to
20, preferably an integer of 1 to 10.
##STR00011##
[0116] Here, R1 to R16 independently represent hydrogen, an alkyl
group having 1 to 12 carbon atoms, an alkoxy group having 1 to 6
carbon atoms, an alkoxycarbonyl group having 2 to 7 carbon atoms,
an aryl group having 6 to 10 carbon atoms, or an aralkyl group
having 7 to 9 carbon atoms. R9 to R16 each may be present at any
position of the benzene rings and, at portions where these
substituents are absent ("*" marks in the formula (II)), the
benzene rings are connected to oxygen in the skeleton of the
formula (I). Note that those compounds of the general formulae (I)
and (II) in which Y is hydrogen, R1 to R16 are each hydrogen, m is
1, and n is 1 are commercially available (trade name "A-BPEF",
manufactured by Shin-Nakamura Chemical Co., Ltd.).
[0117] In addition, from similar viewpoints, (meth)acrylate
represented by the following general formula (III) may be used as
the film of a core material.
##STR00012##
[0118] Here, R.sup.17 is or --CH.sub.2CH(OH)CH.sub.2--,
--(C.sub.2H.sub.4O).sub.hC.sub.2H.sub.4--,
--(C.sub.3H.sub.6O).sub.iC.sub.3H.sub.6--, or
--(C.sub.2H.sub.4O).sub.j--(C.sub.3H.sub.6O).sub.kC.sub.3H.sub.6--,
U is --C(CH.sub.3).sub.2--, --CH.sub.2--, --SO.sub.2--, or --O--, V
is hydrogen or halogen, W is hydrogen or --CH.sub.3. Further, h, i,
j, and k are each an integer of 0 to 10. Among these, bisphenol A
type epoxyacrylate in which R.sup.17 is --CH.sub.2CH(OH)CH.sub.2--,
U is --C(CH.sub.3).sub.2--, V is hydrogen, and W is hydrogen is
particularly preferable. This compound is commercially available
(trade name "EA-1020", manufactured by Shin-Nakamura Chemical Co.,
Ltd.).
[0119] Note that, the above-mentioned fluorene di(meth)acrylate and
a compound having at least one (meth)acryloyl group in the molecule
can be used in combination as the component (B).
[0120] It is preferable that the photopolymerizable compound (B) in
the present invention contain a compound having two or more epoxy
groups in the molecule. Specific examples thereof include:
bifunctional aromatic glycidyl ethers such as a bisphenol A type
epoxy resin, a tetrabromobisphenol A type epoxy resin, a bisphenol
F type epoxy resin, a bisphenol AD type epoxy resin, and a
naphthalene type epoxy resin; polyfunctional aromatic glycidyl
ethers such as a phenol novolak type epoxy resin, a cresol novolak
type epoxy resin, a dicyclopentadiene-phenol type epoxy resin, and
a tetraphenylolethane type epoxy resin; bifunctional aliphatic
glycidyl ethers such as a polyethylene glycol type epoxy resin, a
polypropylene glycol type epoxy resin, a neopentyl glycol type
epoxy resin, and a hexanediol type epoxy resin; bifunctional
alicyclic glycidyl ethers such as a hydrogenated bisphenol A type
epoxy resin; polyfunctional aliphatic glycidyl ethers such as a
trimethylolpropane type epoxy resin, a sorbitol type epoxy resin,
and a glycerol type epoxy resin; bifunctional aromatic glycidyl
esters such as diglycidyl phthalate; bifunctional alicyclic
glycidyl esters such as diglycidyl tetrahydrophthalate and
diglycidyl hexahydrophthalate; bifunctional aromatic glycidylamines
such as N,N-diglycidylaniline and
N,N-diglycidyltrifluoromethylaniline; polyfunctional aromatic
glycidylamines such as
N,N,N',N'-tetraglycidyl-4,4-diaminodiphenylmethane,
1,3-bis(N,N-glycidylaminomethyl)cyclohexane, and
N,N,O-triglycidyl-p-aminophenol; bifunctional alicyclic epoxy
resins such as alicyclic diepoxy acetal, alicyclic diepoxy adipate,
alicyclic diepoxy carboxylate, and vinyl cyclohexene dioxide;
bifunctional heterocyclic epoxy resins such as diglycidyl
hydantoin; polyfunctional heterocyclic epoxy resins such as
triglycidyl isocyanurate; and bifunctional or polyfunctional
silicon-containing epoxy resins such as an organopolysiloxane type
epoxy resin.
[0121] The compounds each having two or more epoxy groups in the
molecule usually have a molecular weight on the order of 100 to
2,000, more preferably 150 to 1,000 and those which are liquid at
room temperature are preferably used. These compounds may be used
singly or two or more of them may be used in combination. Further,
they can be used in combination with other photopolymerizable
compounds. Note that the molecular weight of the photopolymerizable
compound in the present invention can be measured by a GPC method
or a mass spectrometric method.
[0122] The blending amount of the photopolymerizable compound (B)
is preferably 20 to 95 mass % with respect to the total mass of the
components (A) and (B). When the blending amount of the
photopolymerizable compound (B) is 20 mass % or more, it is easy to
cure the resin composition with the base polymer being entangled by
the photopolymerizable compound (B). This is advantageous when
optical waveguides are formed since pattern formability is
increased. On the other hand, when the blending amount is 95 mass %
or less, it is easy to form films by addition of the component (A).
Further, from the viewpoint of easy formation of thick films, the
blending amount is preferably 90 mass % or less. From the
above-mentioned viewpoints, the blending amount of the
photopolymerizable compound (B) is more preferably 30 to 80 mass
%.
[0123] The photopolymerization initiator (C) in the present
invention is not particularly limited. For example, initiators for
fluorene di(meth)acrylates and (meth)acrylates include: aromatic
ketones such as benzophenone,
N,N'-tetramethyl-4,4'-diaminobenzophenone (Michler's ketone),
N,N'-tetraethyl-4,4'-diaminobenzophenone,
4-methoxy-4'-dimethylaminobenzophenone,
2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one,
2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl
ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one,
1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one,
and 1,2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one;
quinones such as 2-ethylanthraquinone, phenanthrenequinone,
2-tert-butylanthraquinone, octamethylanthraquinone,
1,2-benzanthraquinone, 2,3-benzanthraquinone,
2-phenylanthraquinone, 2,3-diphenylanthraquinone,
1-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone,
9,10-phenanthraquinone, 2-methyl-1,4-naphthoquinone, and
2,3-dimethylanthraquinone; benzoin ether compounds such as benzoin
methyl ether, benzoin ethyl ether, and benzoin phenyl ether;
benzoin compounds such as benzoin, methylbenzoin, and ethylbenzoin;
benzyl derivatives such as benzyl dimethyl ketal;
2,4,5-triarylimidazole dimers such as
2-(o-chlorophenyl)-4,5-diphenylimidazole dimer,
2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer,
2-(o-fluorophenyl)-4,5-diphenylimidazole dimer,
2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, and
2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer; phosphine oxides
such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide,
bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and
2,4,6-trimethylbenzoyldiphenylphosphine oxide; acridine derivatives
such as 9-phenylacridine and 1,7-bis(9,9'-acridinyl)heptane;
N-phenylglycine; N-phenylglycine derivatives; and coumarine
compounds. Further, in the case of 2,4,5-triarylimidazole dimers,
two 2,4,5-triarylimidazoles may have the same substituents on the
aryl groups thereof to give a symmetric compound or may have
different substituents on the aryl groups to give an asymmetric
compound. Like the combination of diethylthioxanthone and
dimethylaminobenzoic acid, thioxanthone compounds and tertiary
amine compounds may be combined. These may be used singly or two or
more of them may be used in combination.
[0124] Further, from the viewpoint of increasing transparency of
the core layer and the cladding layer, aromatic ketones and
phosphine oxides from among the above-mentioned compounds are
preferable.
[0125] The initiator for the epoxy resin is not particularly
limited and examples thereof include: aryldiazonium salts such as
p-methoxybenzenediazonium hexafluorophosphate; diaryliodonium salts
such as diphenyliodonium hexafluorophosphonium salt and
diphenyliodonium hexafluoroantimonate; triarylsulfonium salts such
as triphenylsulfonium hexafluorophosphonium salt,
triphenylsulfonium hexafluoroantimonate salt,
diphenyl-4-thiophenoxyphenylsulfonium hexafluoroantimonate,
diphenyl-4-thiophenoxyphenylsulfonium hexafluoroantimonate, and
diphenyl-4-thiophenoxyphenylsulfonium pentafluorohydroxyantimonate;
triallylselenonium salts such as triphenylselenonium
hexafluorophosphonium salt, triphenylselenonium borofluoride, and
triphenylselenonium hexafluoroantimonate; dialkylphenazylsulfonium
salts such as dimethylphenazylsulfonium hexafluoroantimonate and
diethylphenazylsulfonium hexafluoroantimonate;
dialkyl-4-hydroxyphenylsulfonium salts such as
4-hydroxyphenyldimethylsulfonium hexafluoroantimonate and
4-hydroxyphenylbenzylmethylsulfonium hexafluoroantimonate; and
sulfonic acid esters such as
.alpha.-hydroxymethylbenzoinsulfonates, N-hydroxyimidosulfonates,
.alpha.-sulfonyloxyketone, and .beta.-sulfonyloxyketone. These
polymerization initiators may be used singly or two or more of them
may be used in combination.
[0126] The blending amount of the photopolymerization initiator (C)
is preferably 0.1 to 10 mass parts with respect to 100 mass parts
of the total amount of the components (A) and (B). When the
blending amount is 0.1 mass part or more, the photosensitivity of
the resin composition is sufficient while when the blending amount
is 10 mass parts or less, absorption on the surface layer of the
photosensitive resin composition will not increase upon exposure to
light, so sufficient photocuring occurs in the inside the resin
composition. Further, when the resin composition is used as an
optical waveguide, the blending amount is preferably within the
above-mentioned range because transmission loss does not increase
due to the influence of light absorption by the polymerization
initiator itself. From the above-mentioned viewpoints, the blending
amount of the photopolymerization initiator (C) is more preferably
0.2 to 5 mass parts.
[0127] Further, the content of the photopolymerization initiator
(C) is preferably in the range of 0.1 to 10 mass % with respect to
the total mass of the components (B) and (C). On the other hand,
the content of the component (B) is in the range of preferably 90
to 99.9 mass %. When the content of the component (C) is 0.1 mass %
or more, the photosensitivity of the resin composition is
sufficient while when the content of the component (C) is 10 mass %
or less, the surface of the optical waveguide is selectively cured,
so cure will not be insufficient. Further, advantageously,
transmission loss will not increase because of the absorption by
the polymerization initiator itself. From the above-mentioned
viewpoints, the content of the photopolymerization initiator (C) is
more preferably 0.2 to 5 mass %.
[0128] Further, in addition to this, so-called additives such as
inner releasing agents, antioxidants, yellowing preventing agents,
ultraviolet absorbents, visible light absorbing agents, coloring
agents, plasticizers, stabilizers, and fillers may be added to the
resin composition for an optical material of the present invention
as necessary, as far as the effects of the present invention are
not adversely affected.
[0129] The resin film for an optical material of the present
invention is made of the above-mentioned resin composition and when
the film is used as an optical waveguide, it is preferable that the
cured product of the resin composition have optical transmission
loss of 0.5 dB/cm or less. Here, the optical transmission loss is
based on values measured by a prism-coupler type optical
characteristics measuring apparatus (SPA-4000, manufactured by
SAIRON TECHNOLOGY, Inc.).
[0130] The resin film for an optical material of the present
invention can be readily produced by dissolving the resin
composition containing the components (A) to (C) in a solvent,
applying the resultant on a substrate, and removing the solvent.
The solvent used herein is not particularly limited as far as it
can dissolve the resin composition. For example, solvents such as
acetone, methyl ethyl ketone, methyl cellosolve, ethyl cellosolve,
toluene, N,N-dimethylformamide, N,N-dimethylacetamide, and
propylene glycol monomethyl ether and mixed solvents thereof can be
used. The solid concentration in the resin solution is usually on
the order of preferably 30 to 60 mass %.
[0131] The thickness of the resin film for an optical material of
the present invention is not particularly limited and the thickness
after drying is usually 10 .mu.m to 100 .mu.m. When the thickness
of the film is 10 .mu.m or more, the connection tolerance with
light receiving or emitting devices or optical fibers can be
advantageously expanded. On the other hand, when the thickness of
the film is 100 .mu.m or less, the connection efficiency with the
light receiving or emitting devices or optical fibers can be
advantageously increased. From the above-mentioned viewpoints, the
thickness of the film is in the range of more preferably 30 .mu.m
to 70 .mu.m.
[0132] Further, the thickness of the film that serves as a cladding
of an optical waveguide is not particularly limited as far as it
allows containment of light and embedding of the core. Usually, the
thickness of the film is 20 to 200 .mu.m.
[0133] Hereinafter, an application example in which the resin film
for an optical material of the present invention is used as a resin
film for forming an optical waveguide, which is the most preferable
application, will be described in detail.
[0134] The base material used in the process of manufacturing the
resin film for forming optical waveguides of the present invention
is a support for supporting a film for forming optical waveguides,
the material of which is not particularly limited. From the
viewpoints of easy peeling of the film for forming optical
waveguides and heat resistance and solvent resistance, polyesters
such as polyethylene terephthalate, and polyolefins such as
polypropylene and polyethylene are preferably exemplified. The
thickness of the base material is in the range of preferably 5 to
50 .mu.m. When the thickness of the base material is 5 .mu.m or
more, the strength of the support can be advantageously obtained
while when the thickness of the film is 50 .mu.m or less, the gap
between the mask and the pattern upon patterning becomes small so
that finer patterns can be advantageously formed. From the
above-mentioned viewpoints, the thickness of the base material is
in the range of more preferably 10 to 40 .mu.m, further more
preferably 15 to 30 .mu.m, and particularly preferably 20 to 30
.mu.m.
[0135] Further, to increase transmittance of light for exposure and
reduce roughening of the side wall of the core pattern, it is
preferable to use a flexible base material of high transparency
type. A haze value of the base material of high transparency type
is preferably 5% or less, more preferably 3% or less, and
particularly preferably 2% or less. Note that the haze values can
be measured according to JIS K7105 using, for example, a
commercially available turbidity meter such as NDH-1001DP
(manufactured by Nippon Denshoku Industries Co., Ltd.). Such a base
material is available as "Cosmo Shine A1517" and "Cosmo Shine
A4100" (trade names, manufactured by Toyobo Co., Ltd.).
[0136] The film for forming optical waveguides provided on the
thus-obtained base material can be readily stored by winding in the
form of, for example, a roll. Further, a protective film can be
provided on the film for forming optical waveguides as necessary.
Note that the base material and protective film may be subjected to
antistatic treatment or the like for facilitating release of the
film for forming optical waveguides in a later stage.
[0137] The resin film for forming optical waveguides of the present
invention can be used as a lower cladding, a core, and an upper
cladding of an optical waveguide and is preferably used in at least
one of these.
[0138] Hereinafter, the production method of forming optical
waveguides using the resin film will be described in detail. The
method includes, for example, a method in which a lower cladding
film released from the base material is removed of a protective
film, if any, and is pressure-bonded to a substrate with heating to
laminate it. Here, from the viewpoint of adhesion and
followability, it is preferable that the lamination is performed
under reduced pressure. The heating temperature for the resin film
is preferably 50 to 130.degree. C. The pressure at which pressure
bonding is performed is on the order of preferably 0.1 to 1.0 MPa
(on the order of 1 to 10 kgf/cm.sup.2). However, these conditions
are not particularly limited. Then, the lower cladding film is
cured by light or heat. A core film having a higher refractive
index than that of the lower cladding film is laminated in a
similar manner. The laminated resin film thus obtained is
irradiated with actinic radiation through a negative or positive
mask pattern called artwork so that the actinic radiation forms an
image. The light source for actinic radiation includes known light
sources that can effectively radiate ultraviolet ray, for example,
a carbon arc lamp, a mercury vapor arc lamp, a super-high pressure
mercury lamp, a high-pressure mercury lamp, and a Xenon lamp.
Besides, those light sources that effectively radiate visible light
such as a flood lamp for photography and a sunlight lamp can also
be used.
[0139] Then, after exposure to light, wet development, dry
development, or the like is performed to remove unexposed portions
to produce a core pattern. In the case of wet development, a
developer that has a composition corresponding to that of the
above-mentioned resin film, such as an organic solvent, an alkaline
aqueous solution, or a water-based developer is used to perform
development by a known method, for example, by spraying, shaking
immersion, brushing, scrubbing or the like.
[0140] As the developer, organic solvents, alkaline aqueous
solutions, and the like that are safe and stable and user-friendly
ones are preferably used. The above-mentioned organic solvent-based
developers include, for example, 1,1,1-trichloroethane,
N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide,
cyclohexanone, methyl isobutyl ketone, and .gamma.-butyrolactone.
The organic solvents may contain water in a range of 1 to 20 mass %
to prevent catching fire.
[0141] The bases that can be used for the above-mentioned alkaline
aqueous solution include, for example: alkali hydroxides such as
hydroxides of lithium, sodium, or potassium; alkali carbonates such
as carbonates or bicarbonates of lithium, sodium, potassium, or
ammonium; alkali metal phosphates such as potassium phosphate, and
sodium phosphate; and alkali metal pyrophosphates such as sodium
pyrophosphate and potassium pyrophosphate. Examples of a preferable
alkaline aqueous solution used for development include a dilute
solution of 0.1 to 5 mass % sodium carbonate, a dilute solution of
0.1 to 5 mass % potassium carbonate, a dilute solution of 0.1 to 5
mass % sodium hydroxide, and a dilute solution of 0.1 to 5 mass %
sodium tetraborate. Further, it is preferable that the alkaline
aqueous solutions for development have a pH in the range of 9 to
11. The temperature of the alkaline aqueous solution is adjusted
depending on the developability of the layer of the photosensitive
resin composition. The alkaline aqueous solutions may contain
surfactants, defoaming agents, a small amount of organic solvent
for promoting development, and the like.
[0142] The above-mentioned aqueous developer includes water, or an
alkaline aqueous solution and at least one organic solvent. The
alkaline substances besides the above-mentioned substances include,
for example, borax, sodium metasilicate, tetramethylammonium
hydroxide, ethanolamine, ethylenediamine, diethylenetriamine,
2-amino-2-hydroxymethyl-1,3-propanediol, 1,3-diaminopropanol-2, and
morpholine. The pH of the developer is as low as possible within
the range where development of resist can be carried out
sufficiently, and is preferably pH 8 to 12, more preferably pH 9 to
10. Example of the above-mentioned organic solvent include
triacetone alcohol, acetone, ethyl acetate, alkoxyethanol having an
alkoxy group containing 1 to 4 carbon atoms, ethyl alcohol,
isopropyl alcohol, butyl alcohol, diethylene glycol monomethyl
ether, diethylene glycol monoethyl ether, and diethylene glycol
monobutyl ether. These can be used singly or two or more of them
can be used in combination. Preferably, the concentration of the
organic solvents is usually 2 to 90 mass % and the temperature of
the organic solvent can be adjusted depending on the
developability. Further, the aqueous developer may contain
surfactants, defoaming agents, and so on in small amounts.
[0143] Further, two or more developing methods may be used in
combination as necessary. The methods for development include, for
example, a dipping method, a battle method, a spray method such as
a high pressure spray method, brushing, and slapping.
[0144] As a treatment after the development, heating at about 60 to
about 250.degree. C. or exposure to light of about 0.1 to about
1,000 mJ/cm.sup.2 may be performed as necessary to further cure the
core pattern.
[0145] Then, an upper cladding film having a refractive index lower
than that of the core film is laminated in the same manner as
mentioned above to fabricate an optical waveguide.
[0146] Then, the flexible optical waveguide of the present
invention is described. The flexible optical waveguide of the
present invention is fabricated by using a resin film for forming a
core layer having a high refractive index, two resin films for
forming cladding layers having a low refractive index. The flexible
optical waveguide of the present invention is characterized in that
at least one of the resin films for forming cladding layers is
constituted by a resin for forming a cladding layer and a base
material film and the base material film is arranged outside the
cladding layer with respect to the core layer. With this
construction, a flexible optical waveguide to which flexibility and
toughness of the base material film are imparted can be obtained.
Also, use of film-shaped materials for forming optical waveguides
enables to solve the problem of productivity and large area
responsiveness specific to liquid materials. Further, the
construction in which a base material film is arranged outside the
cladding layer avoids exposure of the cladding layer to external
environment, so the optical waveguide becomes less influenced by
contamination or flaws to increase handleability.
[0147] While it is only necessary that the base material film
arranged outside the cladding layer is provided on at least one
side of the flexible optical waveguide, a flexible optical
waveguide having less curling can be fabricated by adopting a
symmetric structure in which the basic material film is provided on
both sides of the optical waveguide.
[0148] The base material film for use in the resin film for forming
a cladding layer used here is a support that imparts flexibility
and toughness to the optical waveguide and its material is not
particularly limited. From the viewpoint of flexibility and
toughness, preferable examples of the material for the base
material film include polyesters such as polyethylene
terephthalate, polybutylene terephthalate, and polyethylene
naphthalate, polyethylene, polypropylene, polyamide, polycarbonate,
polyphenylene ether, polyether sulfide, polyallylate, liquid
crystal polymer, polysulfone, polyether sulfone, polyether ether
ketone, polyether imide, polyamideimide, and polyimide. The
thickness of the base material film may vary depending on the
desired flexibility as appropriate. Preferably, the thickness of
the base material film is 5 .mu.m to 250 .mu.m. The thickness of 5
.mu.m or more is advantageous in that toughness of the base
material film can be easily obtained while the thickness of 250
.mu.m or less provides sufficient flexibility.
[0149] Further, electric wiring may be provided on the base
material film. In this case, a film having provided thereon an
electric wiring in advance may be used as a base material film.
Alternatively, after a flexible optical waveguide is produced, an
electric wiring can be formed on the base material film
thereof.
[0150] The resin film for forming the cladding layer preferably is
prepared such that a film of the resin for forming a cladding layer
is formed on a base material film that is subjected to adhesion
treatment. This enhances the adhesion between the cladding layer
and the base material film to prevent failure in peeling off. The
"adhesion treatment" as used herein refers to a treatment for
increasing adhesion force between the base material film and the
cladding layer resin formed thereon by adhesion promoting resin
coating, corona treatment, matte processing such as sandblasting,
or the like.
[0151] The resin for forming a cladding layer is not limited
particularly as far as it is a resin composition that has a lower
refractive index than that of the core layer and is cured by light
or heat. Thermosetting resin compositions and photosensitive resin
compositions may be used.
[0152] More preferably, the resin for forming a cladding layer is
constituted by a resin composition that includes (A) a base
polymer, (B) a photopolymerizable compound, and (C) a
photopolymerization initiator. Note that, the components (A), (B),
and (C) are as described above.
[0153] The resin film for forming a cladding layer can be prepared
without difficulty by dissolving a resin composition containing the
components (A) to (C) in a solvent, applying the resultant solution
on the base material film, and removing the solvent. The solvent
that can be used in the present invention is the same as that used
in preparing the resin film for an optical material. Note that the
solid concentration in a resin solution is preferably on the order
of preferably 30 to 80 mass %.
[0154] The thickness of the cladding layer after drying is in a
range of preferably 5 .mu.m to 500 .mu.m. The thickness of 5 .mu.m
or more ensures sufficient thickness of cladding that is necessary
for containment of light and the thickness of 500 .mu.m or less
makes it easy to uniformly control the film thickness. From the
above-mentioned viewpoint, the thickness of the cladding layer is
in a range of more preferably 10 .mu.m to 100 .mu.m.
[0155] Further, the thickness of the cladding layer is as follows.
That is, the lower cladding layer that is formed first and the
upper cladding layer that is provided to embed the core pattern
therein may have the same thickness or different thicknesses from
one another. However, it is preferable that the thickness of the
upper cladding layer be made larger than the thickness of the core
layer in order to embed the core pattern in the upper cladding
layer.
[0156] The resin film for forming a core layer used in the present
invention is designed so that the core layer has a higher
refractive index than that of the cladding layer, and a resin
composition that can form a core pattern with actinic radiation can
be used to prepare the resin film for forming a core layer. A
photosensitive resin composition is suitable for this purpose.
Specifically, it is preferable that the same resin composition as
that used for forming the cladding layer be used. That is, a resin
composition that contains the above-mentioned components (A), (B),
and (C) and in addition the above-mentioned optional components as
necessary is preferable.
[0157] The resin film for forming a core layer can be prepared
without difficulty by dissolving a resin composition containing the
components (A) to (C) in a solvent, applying the resultant solution
on the base material film, and removing the solvent. The solvent
that can be used here is the same as that used in preparing the
resin film for an optical material. The solid concentration in the
resin solution is on the order of preferably 30 to 80 mass %.
[0158] The thickness of the resin film for an optical material of
the present invention is not particularly limited and the thickness
after drying is usually 10 .mu.m to 100 .mu.m. When the thickness
of the film is 10 .mu.m or more, the tolerance in alignment when
connection is made to light receiving or emitting devices or
optical fibers after the optical waveguide is formed can be
advantageously expanded. On the other hand, when the thickness of
the film is 100 .mu.m or less, the connection coefficient with the
light receiving or emitting devices or optical fibers after can be
advantageously increased. From the above-mentioned viewpoints, the
thickness of the film is in the range of preferably 30 .mu.m to 70
.mu.m.
[0159] The base material used in the manufacturing process of the
resin film for forming a core layer is a support that supports the
film for forming optical waveguides and is not limited particularly
on the material and may be the same as those described above as the
base material used in the manufacturing process of the resin film
for forming optical waveguides.
[0160] Hereinafter, the method of producing a flexible optical
waveguide according to the present invention is explained in
detail.
[0161] First, in a first step, a cladding layer is formed by curing
a resin for forming a cladding layer in a resin film for forming a
cladding layer, the resin film being constituted by the resin for
forming a cladding layer and a base material film. In the first
step of forming a cladding layer, in case where a protective film
is provided on a side opposite to the base material film in the
resin film for forming a cladding layer, the resin film for forming
a cladding layer is cured with light or heating after the
protective layer is peeled off.
[0162] Then, in a second step, a resin film for forming a core
layer is laminated on the cladding layer to laminate a core layer.
In the second step, the resin film for forming a core layer is
pressure bonded with heating on the above-mentioned cladding layer
to laminate a core layer having refractive index larger than that
of a cladding layer. Here, from the viewpoint of adhesion and
followability, it is preferable that the lamination be performed
under reduced pressure. The heating temperature used here is
preferably set to 50 to 130.degree. C. and the pressure of the
pressure bonding is preferably set to about 0.1 to about 1.0 MPa (1
to 10 kgf/cm.sup.2). However, these conditions are not particularly
limited. The resin film for forming a core layer is easy to handle
and thus is preferable if it is constituted by a core layer and a
base material and it may consist of a core layer alone.
[0163] Then, in a third step, the core layer is exposed to light
and developed to form a core pattern of an optical waveguide.
Specifically, actinic radiation is imagewise irradiated to the core
layer through a negative mask pattern. The light source for actinic
radiation includes known light sources that can effectively radiate
ultraviolet ray, for example, a carbon arc lamp, mercury vapor arc
lamp, a super-high pressure mercury lamp, a high-pressure mercury
lamp, and a Xenon lamp. Besides, those light sources that
effectively radiate visible light such as a flood lamp for
photography and a sunlight lamp can also be used.
[0164] Then, in case where the base material of the resin film for
forming a core layer remains, the base material is peeled off and
then unexposed portions are removed by wet development or the like
to effect development, thus forming a waveguide pattern. In the
case of wet development, a developer that has a composition
corresponding to that of the above-mentioned resin film, such as an
organic solvent is used to perform development, for example, by
spraying, shaking immersion, brushing, scrubbing or the like known
method.
[0165] The organic solvent developer, developing method, and
treatment after development are the same as those mentioned
above.
[0166] After that, a fourth step is performed, which includes
laminating a resin film for forming a cladding layer for embedding
therein a core pattern and curing the film. The lamination is
performed such that in case the resin film for forming a cladding
layer includes a resin for forming a cladding layer and a base
material film, the resin for forming a cladding layer is arranged
on the side of the core pattern. In this case, the thickness of the
cladding layer is preferably made larger than that of the core
layer. Curing is performed by light or heat in the same manner as
mentioned above.
[0167] The above-mentioned production method solves the
conventional problem and greatly shortens the time of fabricating a
multimode optical waveguide having a large core size.
[0168] The resin composition for an optical material that includes
the components (B) and (C) can be obtained by dissolving the
components (B) and (C) in a solvent. The solvent used here is not
particularly limited as far as it can dissolve the resin
composition. Examples of the solvent include N-methylpyrrolidone,
N,N-dimethylformamide, N,N-dimethylacetamide, cyclohexanone, methyl
ethyl ketone, methyl isobutyl ketone, .gamma.-butyrolactone, methyl
cellosolve, ethyl cellosolve, propylene glycol monomethyl ether,
acetone, and toluene. Alternatively, mixed solvents thereof may be
used.
[0169] The resin concentration in the resin solution is usually 30
to 80 mass %.
[0170] The resin composition for an optical material of the present
invention that includes the components (B) and (C) is preferably
used in at least one of the lower cladding, core and upper cladding
of an optical waveguide.
[0171] Hereinafter, the method of fabricating an optical waveguide
using the resin composition for an optical material of the present
invention that includes the components (B) and (C) is explained.
The method involves applying the resin composition on a substrate
using, for example, a spin coating method, a dipping method, a
spraying method, a curtain-coating method, a silk screen method, or
a roll coating method, drying and removing the solvent by heating
or drying under reduced pressure, and then curing the resin by
irradiation of actinic radiation or by heating. The resin layer
constitutes the cladding layer.
[0172] Then, by a similar coating method, a resin composition
having a refractive index higher than that of the earlier formed
optical waveguide layer is applied to form a core layer.
Subsequently, actinic radiation is irradiated through a mask
pattern of negative or positive type. After the exposure to light,
unexposed portions are removed by wet development, dry development
or the like to perform development, whereby a core pattern is
produced. Here, the optical waveguide pattern may be further cured
by heating it at about 60.degree. C. to about 250.degree. C. or
performing exposure at an intensity of about 0.1 to about 1,000
mJ/cm.sup.2 before it can be used.
[0173] After that, a resin having a refractive index lower than
that of the core layer is applied to form a film in the same manner
as mentioned above to fabricate an optical waveguide.
Example
[0174] Then, the present invention will be described in detail by
examples. However, the present invention is by no means limited by
the examples.
Example 1
[0175] Epoxyacrylate oligomer (trade name "HITALLOID", manufactured
by Hitachi Chemical Co., Ltd.) and phenoxy resin (trade name
"YP-50", manufactured by Tohto Kasei Co., Ltd.) were blended in
equivalent mass ratio (using 50 mass parts per 100 mass parts of
total resin of methyl ethyl ketone as a solvent). To this was added
a three-component optical radical generator consisting of an
optical initiator (2,2-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl
1,2'-biimidazole manufactured by Tokyo Chemical Industry Co., Ltd.;
4,4'-bis(diethylamino)benzophenone manufactured by Tokyo Chemical
Industry Co., Ltd., and 2-mercaptobenzimidazole manufactured by
Tokyo Chemical Industry Co., Ltd.) in an amount of 2 mass parts
based on 98 mass parts of total resin to provide a resin
composition for forming an optical waveguide. This was applied on a
PET film ("A4100", manufactured by Toyobo Co., Ltd.) using an
applicator ("YBA-4", manufactured by Yoshimitsu Seiki Co., Ltd.)
and dried under conditions of 80.degree. C. for 10 minutes and then
100.degree. C. for 10 minutes to evaporate the solvent, thereby
obtaining a resin film for optical waveguides. The thickness of the
film could be adjusted between 5 .mu.m and 100 .mu.m by controlling
the gap in the applicator. In this example, the thickness of the
film was adjusted to 12 .mu.m.
[0176] The resin film for forming optical waveguides was laminated
on a silicon wafer (thickness 1 .mu.m) with a thermal oxidation
film (thickness 1 .mu.m) using a vacuum pressure laminator
(MVLP-500, manufactured by Meiki Co., Ltd.) under conditions of a
pressure of 0.4 MPa and a temperature of 60.degree. C. To this was
irradiated ultraviolet ray at an intensity of 1 J/cm.sup.2 from a
metal halide lamp ("Eye Dolphin 3000", manufactured by Eye Graphics
Co., Ltd.) to optically cure the resin. After the PET film was
peeled off, the resin was postbaked under conditions of 160.degree.
C. for 1 hour, thereby obtaining a slab optical waveguide (core
thickness 12 .mu.m). The refractive index of the obtained optical
waveguide (core) was measured using a prism coupler (Model 2020)
manufactured by Metricon Corporation (measuring wavelength 830 nm).
The refractive index obtained was 1.583 for both TE polarized light
and TM polarized light. The slab optical waveguide was passed
through a solder reflow oven ("Salamander", manufactured by
Furukawa Electric Co., Ltd.) three times under conditions of
maximum temperature of 265.degree. C. (retention time of 15 to 20
seconds at 260.degree. C. or more) and nitrogen atmosphere.
[0177] Transmission losses before and after reflow were measured
using a prism coupler optical characteristics measuring apparatus
(SPA-4000, manufactured by SAIRON TECHNOLOGY, INC.) (measuring
wavelength: 830 nm, using matching oil of nD=1.60). As a result,
the transmission losses before and after reflow were found to be
0.2 dB/cm and 0.3 dB/cm, respectively. This indicates that the
resin film for forming optical waveguides had high heat resistance
and low loss. Note that in the present example, the thermal
oxidation film served as a lower cladding and air served as an
upper cladding.
[0178] Further, the gap of the applicator was changed and a 50
.mu.m-thick resin film for forming optical waveguides was prepared
in the same manner as described above. The film was exposed to
light through a mask pattern and developed with
N,N-dimethylacetamide (room temperature, 40 seconds, vibration
shaking) to form a pattern. As a result, fabrication of an optical
waveguide having a line width of 50 .mu.m was confirmed.
Example 2
[0179] A resin film for forming optical waveguides was obtained in
the same manner as that in Example 1 except that solid epoxy resin
(trade name "Epototo YD-7020", manufactured by Tohto Kasei Co.,
Ltd.) was used in place of the phenoxy resin. The thickness of the
film was 12 .mu.m.
[0180] The resin film for forming optical waveguides was treated in
the same manner as in Example 1 to obtain a slab optical waveguide
(core thickness 12 .mu.m). The refractive index of the slab optical
waveguide (core) was measured in the same manner as in Example 1.
As a result, the refractive index was 1.565 for both TE polarized
light and TM polarized light. This was passed through a solder
reflow oven ("Salamander", manufactured by Furukawa Electric Co.,
Ltd.) three times under conditions of a maximum temperature of
265.degree. C. (retention time of 15 to 20 seconds at 260.degree.
C. or more) and nitrogen atmosphere.
[0181] Transmission losses before and after reflow were measured
using a prism coupler optical characteristics measuring apparatus
(SPA-4000, manufactured by SAIRON TECHNOLOGY, INC.) (measuring
wavelength: 830 nm, using matching oil of nD=1.60). As a result,
the transmission losses before and after reflow were found to be
0.2 dB/cm and 0.3 dB/cm, respectively. This indicates that the
resin film for forming optical waveguides had high heat resistance
and low loss.
[0182] Further, the gap of the applicator was changed and a 50
.mu.m-thick resin film for forming optical waveguides was prepared
in the same manner as above. The film was exposed to light through
a mask pattern and developed with N,N-dimethylacetamide (room
temperature, 40 seconds, vibration shaking) to form a pattern. As a
result, fabrication of an optical waveguide having a line width of
50 .mu.m was confirmed.
Example 3
[0183] A resin film for forming optical waveguides was obtained in
the same manner as that in Example 1 except that acryl acrylate
oligomer (trade name "HITALLOID 7975", manufactured by Hitachi
Chemical Co., Ltd.) was used in place of epoxyacrylate oligomer,
and acrylic resin (trade name "HTR-860P-3DR", manufactured by
Teikoku Chemical Industries Co., Ltd.) was used in place of phenoxy
resin. The thickness of the film was 12 .mu.m.
[0184] The resin film for forming optical waveguides was treated in
the same manner as in Example 1 to obtain a slab optical waveguide
(core thickness 12 .mu.m). The refractive index of the slab optical
waveguide (core) was measured in the same manner as in Example 1.
As a result, the refractive index was 1.505 for both TE polarized
light and TM polarized light. This was passed through a solder
reflow oven ("Salamander", manufactured by Furukawa Electric Co.,
Ltd.) three times under conditions of a maximum temperature of
265.degree. C. (retention time of 15 to 20 seconds at 260.degree.
C. or more) and nitrogen atmosphere.
[0185] Transmission losses before and after reflow were measured
using a prism coupler optical characteristics measuring apparatus
(SPA-4000, manufactured by SAIRON TECHNOLOGY, INC.) (measuring
wavelength: 830 nm, using matching oil of nD=1.56). As a result,
the transmission losses before and after reflow were found to be
0.2 dB/cm and 0.3 dB/cm, respectively. This indicates that the
resin film for forming optical waveguides had high heat resistance
and low loss.
[0186] Further, the gap of the applicator was changed and a 50
.mu.m-thick resin film for forming optical waveguides was prepared
in the same manner as above. The film was exposed to light through
a mask pattern and developed with N,N-dimethylacetamide (room
temperature, 40 seconds, vibration shaking) to form a pattern. As a
result, fabrication of an optical waveguide having a line width of
50 .mu.m was confirmed.
Example 4
[0187] Epoxy resin having two or more epoxy groups in the molecule
(trade name "KRM-2110", manufactured by Adeka Corporation) and a
phenoxy resin (trade name "YP-50", manufactured by Tohto Kasei Co.,
Ltd., 35% methyl ethyl ketone solution) were blended in amounts of
70.4 mass % and 29.6 mass %, respectively and then the mixture was
blended with a photopolymerization initiator (trade name "SP-170",
manufactured by Adeka Corporation) in an amount of 2 mass parts per
100 mass parts of the resin components to provide a resin
composition for forming optical waveguides. The resultant was
applied on a polyester film (trade name "A4100", manufactured by
Toyobo Co., Ltd.) using an applicator ("YBA-4", manufactured by
Yoshimitsu Seiki Co., Ltd.) and dried under conditions of
80.degree. C. for 10 minutes and then 100.degree. C. for 10 minutes
to evaporate the solvent, thereby obtaining a resin film for
optical waveguides. The thickness of the film on this occasion
could be adjusted between 5 .mu.m and 100 .mu.m by controlling the
gap in the applicator. In this example, the thickness of the film
was adjusted to 12 .mu.m.
[0188] The resin film for forming optical waveguides was laminated
on a silicon wafer (thickness 1 .mu.m) with a thermal oxidation
film (thickness 1 .mu.m) using a vacuum pressure laminator
(MVLP-500, manufactured by Meiki Co., Ltd.) under conditions of a
pressure of 0.4 MPa and a temperature of 60.degree. C. The
resultant was irradiated with ultraviolet ray at an intensity of 1
J/cm.sup.2 by means of "EXM-7172-B-00" (manufactured by ORC
manufacturing Co., Ltd.) to optically cure the resin. Then, the
resin was postbaked under conditions of 160.degree. C. for 1 hour
to obtain a slab optical waveguide (core thickness 12 .mu.m). The
refractive index of the obtained optical waveguide (core) was
measured in the same manner as in Example 1. As a result, the
refractive index obtained was 1.537 for both TE polarized light and
TM polarized light. The slab optical waveguide was passed through a
solder reflow oven ("Salamander", manufactured by Furukawa Electric
Co., Ltd.) three times under conditions of maximum temperature of
265.degree. C. (retention time of 15 to 20 seconds at 260.degree.
C. or more) and nitrogen atmosphere.
[0189] Optical transmission losses before and after reflow were
measured using a prism coupler optical characteristics measuring
apparatus (SPA-4000, manufactured by SAIRON TECHNOLOGY, INC.)
(measuring wavelength: 830 nm, using matching oil of nD=1.56). As a
result, the optical transmission losses before and after reflow
were found to be 0.1 dB/cm. This indicates that the resin film for
forming optical waveguides had high heat resistance and low loss.
Note that in the present example, the thermal oxidation film served
as a lower cladding and air served as an upper cladding.
[0190] Further, the gap of the applicator was changed and a 50
.mu.m-thick resin film for forming optical waveguides was prepared
in the same manner as above. The film was exposed to light through
a mask pattern and developed with N,N-dimethylformamide (room
temperature, 40 seconds, vibration shaking) to form a pattern. As a
result, fabrication of an optical waveguide having a line width of
50 .mu.m was confirmed. The results are shown in Table 1.
Example 5
[0191] A resin film for forming optical waveguides was obtained in
the same manner as that in Example 1 except that the epoxy resin
having two or more epoxy groups in the molecule was replaced by
"KRM-2199" trade name, manufactured by Adeka Corporation, and
evaluated similarly. Note that the refractive index of the slab
optical waveguide (core) was measured in the same manner as in
Example 1, the refractive index was 1.529 for both TE polarized
light and TM polarized light.
[0192] Optical transmission losses before and after reflow were
measured using a prism coupler optical characteristics measuring
apparatus (SPA-4000, manufactured by SAIRON TECHNOLOGY, INC.)
(measuring wavelength: 830 nm, using matching oil of nD=1.56). As a
result, the optical transmission losses before and after reflow
were found to be 0.1 dB/cm and 0.3 dB/cm, respectively. This
indicates that the resin film for forming optical waveguides had
high heat resistance and low loss.
[0193] Further, in the same manner as in Example 4, it was
confirmed that an optical waveguide having a line width of 50 .mu.m
could be fabricated. The results are shown in Table 1.
Example 6
[0194] A resin film for forming optical waveguides was obtained in
the same manner as that in Example 4 except that the epoxy resin
having two or more epoxy groups in the molecule was replaced by
"KRM-2408" trade name, manufactured by Adeka Corporation, and
evaluated similarly. Note that the refractive index of the slab
optical waveguide (core) was measured in the same manner as in
Example 1, the refractive index was 1.532 for both TE polarized
light and TM polarized light.
[0195] Optical transmission losses before and after reflow were
measured using a prism coupler optical characteristics measuring
apparatus (SPA-4000, manufactured by SAIRON TECHNOLOGY, INC.)
(measuring wavelength: 830 nm, using matching oil of nD=1.56). As a
result, the optical transmission losses before and after reflow
were found to be 0.1 dB/cm and 0.2 dB/cm, respectively. This
indicates that the resin film for forming optical waveguides had
high heat resistance and low loss.
[0196] Further, in the same manner as in Example 4, it was
confirmed that an optical waveguide having a line width of 50 .mu.m
could be fabricated. The results are shown in Table 1.
Example 7
[0197] A resin film for forming optical waveguides was obtained in
the same manner as that in Example 4 except that the base polymer
was replaced by "YD-7020" trade name, manufactured by Tohto Kasei
Co., Ltd. (solid epoxy resin at room temperature), and evaluated
similarly. Note that the refractive index of the slab optical
waveguide (core) was measured in the same manner as in Example 1,
the refractive index was 1.573 for both TE polarized light and TM
polarized light.
[0198] Optical transmission losses before and after reflow were
measured using a prism coupler optical characteristics measuring
apparatus (SPA-4000, manufactured by SAIRON TECHNOLOGY, INC.)
(measuring wavelength: 830 nm, using matching oil of nD=1.60). As a
result, the optical transmission losses before and after reflow
were found to be 0.2 dB/cm and 0.3 dB/cm, respectively. This
indicates that the resin film for forming optical waveguides had
high heat resistance and low loss.
[0199] Further, in the same manner as in Example 4, it was
confirmed that an optical waveguide having a line width of 50 .mu.m
could be fabricated. The results are shown in Table 1.
Comparative Example 1 to 3
[0200] Preparation of resin films for forming optical waveguides in
the same manner as in Examples 4 to 6, respectively, was attempted
except that a base polymer not used in Examples 4 to 6. In each
case, after the solvent was evaporated, no films could be formed
from the resins and remained liquid. The results obtained are shown
in Table 1.
TABLE-US-00001 TABLE 1 Optical transmission (A) (B) (C) loss
(dB/cm) Base Photopolymerizable Polymerization Film Before After
polymer Compound initiator formability reflow reflow Example 4
YP-50 KRM-2110 SP-170 Possible 0.1 0.1 (29.6 mass %) (70.4 mass %)
(2 Mass part) Example 5 YP-50 KRM-2199 SP-170 Possible 0.1 0.3
(29.6 mass %) (70.4 mass %) (2 Mass part) Example 6 YP-50 KRM-2408
SP-170 Possible 0.1 0.2 (29.6 mass %) (70.4 mass %) (2 Mass part)
Example 7 YP-7020 KRM-2110 SP-170 Possible 0.2 0.3 (29.6 mass %)
(70.4 mass %) (2 Mass part) Comparative None KRM-2110 SP-170
Impossible -- -- example 1 (100 Mass part) (2 Mass part)
Comparative None KRM-2199 SP-170 Impossible -- -- example 2 (100
Mass part) (2 Mass part) Comparative None KRM-2408 SP-170
Impossible -- -- example 3 (100 Mass part) (2 Mass part)
Example 8
[0201] Using the composition shown in Table 2, resins for a core
and a cladding, respectively, were provided. Methyl ethyl ketone as
a solvent was added in an amount of 40 mass parts based on the
total amount to prepare resin varnishes for a core and a cladding,
respectively. Those were applied on a PET film ("A4100",
manufactured by Toyobo Co., Ltd.) using an applicator ("YBA-4",
manufactured by Yoshimitsu Seiki Co., Ltd.) and dried under
conditions of 80.degree. C. for 10 minutes and then 100.degree. C.
for 10 minutes to evaporate the solvent, thereby obtaining a resin
film for optical waveguides. The thickness of the film could be
adjusted between 5 .mu.m and 100 .mu.m by controlling the gap in
the applicator. In this example, the thicknesses of the films after
the curing were adjusted such that the core film was 50 .mu.m
thick, the lower cladding was 30 .mu.m thick, and the upper
cladding was 80 .mu.m thick. Note that the refractive indices of
the core film and cladding film were measured in the same manner as
in Example 1 (measuring wavelength: 830 nm) to find that the core
film had a refractive index of 1.586 and the cladding film had a
refractive index of 1.537.
[0202] The lower cladding film was laminated on an FR-4 substrate
(trade name "E-679F", manufactured by Hitachi Chemical Co., Ltd.)
using a vacuum pressure laminator (MVLP-500, manufactured by Meiki
Co., Ltd.) under conditions of a pressure of 0.5 MPa and a
temperature of 50.degree. C. for a pressurization time of 30
seconds. Then, to this was irradiated ultraviolet ray (wavelength
365 nm) at an intensity of 1000 mJ/cm.sup.2 by an ultraviolet
exposure device ("EXM-1172", manufactured by ORC manufacturing Co.,
Ltd.) to form a lower cladding (FIG. 1(a)). Then, on the lower
cladding, a core film was laminated using the above-mentioned
vacuum pressure laminator under conditions of a pressure of 0.5 MPa
and a temperature of 50.degree. C. for a pressurization time of 30
seconds (FIG. 1(b)). Subsequently, ultraviolet ray (wavelength 365
nm) was irradiated at an intensity of 1000 mJ/cm2 through a photo
mask using the above-mentioned ultraviolet exposure device (FIG.
1(c)). Thereafter, the core pattern was developed using
N,N-dimethylacetamide as a solvent (FIG. 1(d)). To clean the
developer, methanol and water were used.
[0203] Then, an upper cladding was formed in the same conditions as
those for forming the lower cladding. Finally, heat treatment was
performed at 160.degree. C. to fabricate an optical waveguide (FIG.
1(e)).
[0204] The transmission loss of the optical waveguide thus obtained
were measured using a 855-nm LED ("Q81201", manufactured by
Advantest Corporation) as a light source and a light receiving
sensor ("Q82214", manufactured by Advantest Corporation) by a
cut-back method (measured waveguide wavelength 5, 3, and 2 cm,
input fiber; GI-50/125 multimode fiber (NA=0.20), output fiber;
SI-114/125 (NA=0.22), input light; effective core diameter 26
.mu.m) to find 0.3 dB/cm. Further, the fabricated optical waveguide
were passed through a solder reflow oven ("Salamander",
manufactured by Furukawa Electric Co., Ltd.) three times under
conditions of a maximum temperature of 265.degree. C. (retention
time of 15 to 20 seconds at 260.degree. C. or more) and nitrogen
atmosphere, and loss degradation by reflow was measured. As a
result, no increase in loss by reflow was observed. This indicated
that the optical waveguide fabricated using the resin film for
forming optical waveguides of the present invention had high heat
resistance and low loss.
[0205] Further, checking the pattern formability of the resin film
confirmed that fine patterns with line/space of 30/95 .mu.m, 40/85
.mu.m, and 50/75 .mu.m could be formed (Table 3).
TABLE-US-00002 TABLE 2 (B) Photopolymerizable (A) Base polymer
compound (C) Polymerization initiator For core Phenototo
YP-70*.sup.1 A-BPEF*.sup.2 2,2-Bis(2-chlorophenyl)- (20.4 mass %)
(39.8 mass %) 4,4',5,5'-tetraphenyl 1,2'- biimidazole*.sup.5 (1
mass part) EA-1020*.sup.3 4,4'- (39.8 mass %)
Bis(diethylamino)benzophenone*.sup.6 (0.5 mass parts)
2-Mercaptobenzimidazole*.sup.7 (0.5 mass parts) For Phenototo
YP-70*.sup.1 KRM-2110*.sup.4 SP-170*.sup.8 cladding (35.7 mass %)
(64.3 mass %) (2 mass parts) *.sup.1Phenototo YP-70; Phenoxy resin
(manufactured by Tohto Kasei Co., Ltd.), bisphenol A/bisphenol F
copolymer type phenoxy resin *.sup.2A-BPEF; fluorene diacrylate
(manufactured by Shin-Nakamura Chemical Co., Ltd.),
9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene *.sup.3EA-1020;
bisphenol A type epoxyacrylate (manufactured by Shin-Nakamura
Chemical Co., Ltd.), bisphenol A type epoxyacrylate
*.sup.4KRM-2110; 2-functional alicyclic epoxy resin (manufactured
by Adeka Corporation), alicyclic diepoxy carboxylate
*.sup.52,2-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole;
manufactured by Tokyo Chemical Industry Co., Ltd.
*.sup.64,4'-Bis(diethylamino)benzophenone; manufactured by Tokyo
Chemical Industry Co., Ltd. *.sup.72-Mercaptobenzimidazole;
manufactured by Tokyo Chemical Industry Co., Ltd. *.sup.8SP-170;
triphenylsulfonium hexafluoroantimonate
Example 9
[0206] A flexible optical waveguide was fabricated in the same
manner as that in Example 8 except that for the photopolymerization
initiator (C) for core in Table 2,
bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (1 mass part,
manufactured by Ciba Specialty Chemicals) was replaced by
1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one (1
mass part, manufactured by Chiba Specialty Chemicals), and the
irradiation dose of ultraviolet ray upon exposure of the core
pattern was changed to 400 mJ/cm.sup.2. Note that in this case, the
refractive index of the core layer measured using a prism coupler
(Model 2020) manufactured by Metricon Corporation was 1.582.
[0207] The transmission loss of the optical waveguide thus obtained
was measured by the cut-back method in the same manner as in
Example 8 (measured waveguide wavelength 5, 3, and 2 cm, input
fiber; GI-50/125 multimode fiber (NA=0.20), output fiber;
SI-114/125 (NA=0.22), input light; effective core diameter 26
.mu.m) was 0.1 dB/cm. This indicated that when the initiator in
this example was used, the obtained optical waveguide had a very
high transparency. Further, loss deterioration due to reflow was
measured in the same manner as in Example 8, which gave an increase
in loss of below 0.1 dB/cm, confirming that the fabricated optical
waveguide had high heat resistance.
Reference Example 1
[0208] A flexible optical waveguide was fabricated in the same
manner as that in Example 8 except that Phenototo YP-70 was
replaced by Phenototo YP-50 (bisphenol A type epoxy resin,
manufactured by Tohto Kasei Co., Ltd.). The transmission loss of
the flexible optical waveguide was 0.3 dB/cm and no increase in
loss due to reflow was observed. However, patterns at a line/space
of 30 .mu.m/95 .mu.m, and 50 .mu.m/75 .mu.m could not be formed
(Table 3). The pattern at a line/space of 30 .mu.m/95 .mu.m showed
peeling of core due to insufficient cladding/core interface
adhesion while the pattern at a line/space of 50 .mu.m/75 .mu.m
showed development residue due to low solubility of unexposed
portions.
TABLE-US-00003 TABLE 3 Transmission loss (dB/cm) Before After
Pattern formability (line/space) reflow reflow 30/95 (.mu.m) 40/85
(.mu.m) 50/75 (.mu.m) Example 8 0.3 0.3 Possible Possible Possible
Reference 0.3 0.3 Impossible Possible Impossible example 1
Example 10
[0209] To fluorene diacrylate (trade name "A-BPEF", manufactured by
Shin-Nakamura Chemical Co., Ltd.) was added 2 mass % of a
photopolymerization initiator (a three-component optical radical
generator consisting of
"2,2-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl 1,2'-biimidazole"
manufactured by Tokyo Chemical Industry Co., Ltd.);
"4,4'-bis(diethylamino)benzophenone" manufactured by Tokyo Chemical
Industry Co., Ltd., and "2-mercaptobenzimidazole" manufactured by
Tokyo Chemical Industry Co., Ltd.) and N,N-dimethylacetamide as a
solvent in an amount of 30 mass parts per total 100 mass parts of
fluorene diacrylate and the optical initiator to provide a resin
composition for forming optical waveguides. Then, a resin layer was
formed on a silicon wafer (thickness 1 .mu.m) with a thermal
oxidation film (thickness 1 .mu.m) by a spin coating method and
dried under conditions of 80.degree. C. for 10 minutes and then
100.degree. C. for 10 minutes to evaporate and remove the solvent.
Subsequently, the resultant resin layer was irradiated with
ultraviolet ray at an intensity of 1 J/cm.sup.2 from a
high-pressure mercury lamp to optically cure the resin. Further,
the resin was postbaked under conditions of 160.degree. C. for 1
hour to obtain a slab optical waveguide (core thickness 10 .mu.m).
The refractive index of the obtained slab optical waveguide (core)
was measured in the same manner as in Example 1, thereby observing
a refractive index of 1.613 for both TE polarized light and TM
polarized light. Further, measurement of the slab optical waveguide
using TGD-7000, manufactured by ULVAC indicated that the slab
optical waveguide had a thermal decomposition temperature of about
300.degree. C., confirming that it had high heat resistance.
[0210] The slab optical waveguide was passed through a solder
reflow oven ("Salamander", manufactured by Furukawa Electric Co.,
Ltd.) three times under conditions of maximum temperature of
265.degree. C. (retention time of 15 to 20 seconds at 260.degree.
C. or more) and nitrogen atmosphere. Transmission losses before and
after reflow were measured using a prism coupler optical
characteristics measuring apparatus (SPA-4000, manufactured by
SAIRON TECHNOLOGY, INC.) (measuring wavelength: 830 nm, using
matching oil of nD=1.62). As a result, the transmission losses
before and after reflow were found to be 0.1 dB/cm and 0.1 dB/cm,
respectively. This indicates that the resin film for forming
optical waveguides had high heat resistance and low loss. Note that
in the present example, the thermal oxidation film served as a
lower cladding and air served as an upper cladding.
Example 11
[0211] To fluorene diacrylate (trade name "A-BPEF", manufactured by
Shin-Nakamura Chemical Co., Ltd.) was added as a base polymer, a
phenoxy resin (trade name "Phenototo YP-50", manufactured by Tohto
Kasei Co., Ltd.) such that fluorene diacrylate was in an amount of
80 mass % and the phenoxy resin was in an amount of 20 mass %, as
well as an optical initiator in an amount of 2 mass parts per total
100 mass parts of the resins (a three-component optical radical
generator consisting of
"2,2-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl 1,2'-biimidazole"
manufactured by Tokyo Chemical Industry Co., Ltd.);
"4,4'-bis(diethylamino)benzophenone" manufactured by Tokyo Chemical
Industry Co., Ltd., and "2-mercaptobenzimidazole" manufactured by
Tokyo Chemical Industry Co., Ltd.). To the resultant was added 40
mass parts of methyl ethyl ketone as a solvent to provide a resin
composition for forming optical waveguides. The resin composition
was applied on a PET film ("A4100", manufactured by Toyobo Co.,
Ltd.) using an applicator ("YBA-4", manufactured by Yoshimitsu
Seiki Co., Ltd.) and dried under conditions of 80.degree. C. for 10
minutes and then 100.degree. C. for 10 minutes to evaporate and
remove the solvent, thereby obtaining a resin film for optical
waveguides. The thickness of the resin film for optical waveguides
could be adjusted between 5 .mu.m and 100 .mu.m by controlling the
gap in the applicator. In this example, the thickness of the resin
film was adjusted to 12 .mu.m.
[0212] The resin film for forming optical waveguides was laminated
on a silicon wafer (thickness 1 .mu.m) with a thermal oxidation
film (thickness 1 .mu.m) using a vacuum pressure laminator
(MVLP-500, manufactured by Meiki Co., Ltd.) under conditions of a
pressure of 0.4 MPa and a temperature of 60.degree. C. To this was
irradiated ultraviolet ray at an intensity of 1 J/cm.sup.2 by an
ultraviolet exposure device ("EXM-7172", manufactured by ORC
manufacturing Co., Ltd.) to optically cure the resin and then post
baking was performed under conditions of at 160.degree. C. for 1
hour to obtain a slab optical waveguide (core thickness 12 .mu.m).
The refractive index of the obtained slab optical waveguide (core)
was measured in the same manner as in Example 1, thereby obtaining
a refractive index of 1.607 for both TE polarized light and TM
polarized light. The slab optical waveguide was passed through a
solder reflow oven ("Salamander", manufactured by Furukawa Electric
Co., Ltd.) three times under conditions of maximum temperature of
265.degree. C. (retention time of 15 to 20 seconds at 260.degree.
C. or more) and nitrogen atmosphere.
[0213] Transmission losses before and after reflow were measured
using a prism coupler optical characteristics measuring apparatus
(SPA-4000, manufactured by SAIRON TECHNOLOGY, INC.) (measuring
wavelength: 830 nm, using matching oil of nD=1.62). As a result,
the transmission losses before and after reflow were found to be
0.2 dB/cm and 0.2 dB/cm, respectively. This indicates that the
resin film for forming optical waveguides had high heat resistance
and low loss.
Example 12
[0214] A slab optical waveguides was obtained in the same manner as
that in Example 11 except that solid epoxy resin at room
temperature (trade name "Epototo YD-7020", manufactured by Tohto
Kasei Co., Ltd.) was used in place of the phenoxy resin in Example
11. The refractive index of the slab optical waveguide (core) was
measured in the same manner as in Example 1. As a result, the
refractive index was 1.604 for both TE polarized light and TM
polarized light. This was passed through a solder reflow oven
("Salamander", manufactured by Furukawa Electric Co., Ltd.) three
times under conditions of a maximum temperature of 265.degree. C.
(retention time of 15 to 20 seconds at 260.degree. C. or more) and
nitrogen atmosphere. Transmission losses before and after reflow
were measured using a prism coupler optical characteristics
measuring apparatus (SPA-4000, manufactured by SAIRON TECHNOLOGY,
INC.) (measuring wavelength: 830 nm, using matching oil of
nD=1.62). As a result, the transmission losses before and after
reflow were found to be 0.2 dB/cm and 0.2 dB/cm, respectively. This
indicates that the resin film for forming optical waveguides had
high heat resistance and low loss.
Example 13
[0215] Using the composition shown in Table 2, resin compositions
for a core and a cladding, respectively, were provided. Ethyl
cellosolve as a solvent was added in an amount of 40 mass parts
based on the total amount to prepare resin varnishes for a core and
a cladding, respectively.
[0216] These were applied on a PET film ("Cosmo Shine A1517",
manufactured by Toyobo Co., Ltd., thickness 16 .mu.m) using an
applicator ("YBA-4", manufactured by Yoshimitsu Seiki Co., Ltd.)
(resin film for forming a cladding layer: a wound adhesive-treated
surface was used, resin film for forming a core layer: a unwound
non-treated surface was used) and dried under conditions of
80.degree. C. for 10 minutes and then 100.degree. C. for 10 minutes
to dry the solvent, thereby obtaining resin films for forming a
core layer and cladding layer, respectively. The thickness of the
film could be adjusted between 5 .mu.m and 100 .mu.m by controlling
the gap in the applicator. In this example, the thicknesses of the
films after the curing were adjusted such that the core film was 40
.mu.m thick, the lower cladding was 20 .mu.m thick, and the upper
cladding was 70 .mu.m thick.
[0217] To this was irradiated ultraviolet ray at an intensity of
1000 mJ/cm.sup.2 by an ultraviolet exposure device ("EXM-1172",
manufactured by ORC manufacturing Co., Ltd.) to optically cure the
resin (FIG. 2(a)). Then, a resin film for forming a core layer was
laminated on the cladding layer using a vacuum pressure laminator
(MVLP-500, manufactured by Meiki Co., Ltd.) under conditions of a
pressure of 0.4 MPa, a temperature of 70.degree. C., and a pressure
time of 30 seconds (see, FIG. 2(b)). Subsequently, this was
irradiated with ultraviolet ray at an intensity of 1000 mJ/cm.sup.2
through a photo mask (negative type) of 40 .mu.m in width using the
above-mentioned ultraviolet exposure device (wavelength 365 nm)
(see, FIG. 2(c)), and then the core pattern was developed with a
mixed solvent consisting of 8:2 mixture of ethyl cellosolve and
N,N-dimethylacetamide (see, FIG. 2(d)). To clean the developer,
methanol and water were used. Then, a resin film for forming an
upper cladding was laminated on the core pattern under similar
lamination conditions, irradiated with ultraviolet ray, and
heat-treated at 110.degree. C. to fabricate a flexible optical
waveguide (see, FIG. 2(e)).
[0218] Note that the refractive index of the core layer and the
cladding layer was measured using a prism coupler (Model 2010)
manufactured by Metricon Corporation at a wavelength of 850 nm. The
refractive index obtained was 1.584 for the core layer and 1.537
for the cladding layer.
[0219] The transmission loss of the flexible optical waveguide was
measured using a 855-nm LED ("Q81201", manufactured by Advantest
Corporation) as a light source by a cut-back method (measured
waveguide wavelengths of 5, 3, and 2 cm, input fiber; GI-50/125
multimode fiber (NA=0.20), output fiber; SI-114/125 (NA=0.22),
input light; effective core diameter 26 .mu.m), thereby observing
0.3 dB/cm.
[0220] Further, winding flexibility around a pole having radius of
2 mm and toughness were examined. The results showed that neither
cracks were observed in the optical waveguide nor interface
separation between the cladding layer and the core layer occurred,
thus indicating that the optical waveguide had high flexibility and
toughness.
Example 14
[0221] An optical waveguide was fabricated in the same manner as in
Example 13 except that the photopolymerization initiator (C) for
core in Table 4 was changed to
bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (1 mass part,
manufactured by Ciba Specialty Chemicals)
1-[4-(2-hydroxyethoxy)phenyl] and
-2-hydroxy-2-methyl-1-propan-1-one (1 mass part, manufactured by
Ciba Specialty Chemicals), and the irradiation dose of ultraviolet
ray upon exposure of the core pattern was changed to 400
mJ/cm.sup.2. The refractive index of the core layer measured using
a prism coupler (Model 2010) manufactured by Metricon Corporation
was 1.582.
[0222] The transmission loss of the flexible optical waveguide thus
obtained measured in the same manner as in Example 13 was found to
be 0.1 dB/cm, indicating that use of an initiator in this example
provided very high transparency.
Example 15
[0223] Using the composition shown in Table 4, resin compositions
for a core and a cladding, respectively, were provided. Ethyl
cellosolve as a solvent was added in an amount of 40 mass parts
based on the total amount to prepare resin varnishes for a core
layer and a cladding layer, respectively.
TABLE-US-00004 TABLE 4 (B) Photopolymerizable (C) Polymerization
(A) Base polymer compound initiator Core Phenototo YP-70*.sup.1
A-BPEF*.sup.2 Bis(2,4,6- (20 mass parts) (39 mass parts)
trimethylbenzoyl)phenylphosphine oxide*.sup.9 (1 mass part)
EA-1020*.sup.3 1-[4-(2-Hydroxyethoxy)phenyl]- (39 mass parts)
2-hydroxy-2-methyl-1-propan-1- one*.sup.10(1 mass part) Cladding
Phenototo YP-70*.sup.1 KRM-2110*.sup.4 SP-170*.sup.8 (2 mass parts)
(35 mass parts) (62.5 mass parts) SP-100*.sup.11 (0.5 mass parts)
*1 to *4 and *8 Above mentioned.
*.sup.9Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide;
manufactured by Ciba Specialty Chemicals
*.sup.101-[4-(2-Hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one;
manufactured by Ciba Specialty Chemicals *.sup.11SP-100; aromatic
compound, manufactured by Adeka Corporation.
[0224] The varnish for forming a cladding layer was applied on a
corona-discharge-treated surface of a polyamide film (trade name
"Mictron", manufactured by Toray Industries, Inc., 12 .mu.m thick)
and the varnish for forming a core was applied on a non-treated
surface of a PET film (trade name "Cosmo Shine A1517", manufactured
by Toyobo Co., Ltd., 16 .mu.m thick) using an applicator (trade
name "YBA-4", manufactured by Yoshimitsu Seiki Co., Ltd.) and the
solvent was dried at 80.degree. C. for 10 minutes and then
100.degree. C. for 10 minutes to obtain resin films for forming a
core layer and a cladding layer. The thickness of the films on this
occasion could be adjusted between 5 .mu.m and 100 .mu.m by
controlling the gap in the applicator. In this example, the
thickness of the films after curing was adjusted to 40 .mu.m for
the core layer, 20 .mu.m for the lower cladding layer, and 70 .mu.m
for the upper cladding layer.
[0225] To this was irradiated ultraviolet ray at an intensity of
1000 mJ/cm.sup.2 by an ultraviolet exposure device ("EXM-1172",
manufactured by ORC manufacturing Co., Ltd.) to optically cure the
resin (FIG. 2(a)). Then, a resin film for forming a core layer was
laminated on the cladding layer using a vacuum pressure laminator
(MVLP-500, manufactured by Meiki Co., Ltd.) under conditions of a
pressure of 0.4 MPa, a temperature of 70.degree. C. and a pressure
time of 30 seconds (see, FIG. 2(b)). Subsequently, this was
irradiated with ultraviolet ray at an intensity of 400 mJ/cm.sup.2
through a photo mask (negative type) of 40 .mu.m in width using the
above-mentioned ultraviolet exposure device (see, FIG. 2(c)), and
then the core pattern was developed with a mixed solvent consisting
of 8:2 mixture of ethyl cellosolve and N,N-dimethylacetamide (see,
FIG. 2(d)). To clean the developer, methanol and water were used.
Then, a resin film for forming an upper cladding was laminated on
the core pattern under similar lamination conditions, irradiated
with ultraviolet ray by using "Eyedolphin 3000" (manufactured by
Eye graphics Co., Ltd.) (wavelength 405 nm), and then heat-treated
at 160.degree. C. to fabricate a flexible optical waveguide (see,
FIG. 2(e)).
[0226] Note that the refractive index of the obtained optical
waveguide was measured using a prism coupler (Model 2010)
manufactured by Metricon Corporation at a wavelength of 850 nm. The
refractive index obtained was 1.582 for the core layer and 1.539
for the cladding layer.
[0227] The transmission loss of the flexible optical waveguide was
measured using a 855-nm LED ("Q81201", manufactured by Advantest
Corporation) as a light source by a cut-back method (measured
waveguide wavelengths of 5, 3, 2 cm, input fiber; GI-50/125
multimode fiber (NA=0.20), output fiber; SI-114/125 (NA=0.22),
input light; effective core diameter 26 .mu.m), thereby observing
0.1 dB/cm and extremely low loss.
[0228] Further, the fabricated flexible optical waveguide was
passed through a solder reflow oven ("Salamander", manufactured by
Furukawa Electric Co., Ltd.) three times under conditions of a
maximum temperature of 265.degree. C. (retention time of 15 to 20
seconds at 260.degree. C. or more) and nitrogen atmosphere, and an
increase in loss by reflow was measured. As a result, an increase
in loss by reflow was found to be below 0.1 dB/cm. This indicated
that when polyamide was used as the base material film, the
resultant flexible optical waveguide had high heat resistance.
[0229] Further, winding flexibility around a pole having radius of
2 mm and toughness were examined. The results showed that neither
cracks were observed in the optical waveguide nor interface
separation between the cladding layer and the base material film or
between the cladding layer and the core layer occurred, thus
indicating that the optical waveguide had high flexibility and
toughness.
Example 16
[0230] A flexible optical waveguide was fabricated in the same
manner as that in Example 13 except that the resin film for forming
a cladding was applied to the unwound (non-treated surface) of a
PET film. In this case, when the obtained flexible optical
waveguide was wound around a pole having a radius of 2 mm, some
peeling occurred on the interface between the cladding layer and
the base material film and cracks occurred on the flexible optical
waveguide. However, the flexible optical waveguide had sufficient
flexibility and toughness for practical purposes.
Example 17
[0231] The core film and cladding film (both 10 .mu.m thick)
prepared in the same manner as that in Example 8 were measured for
refractive index and birefringence using a prism coupler (Model
2020) manufactured by Metricon Corporation. The results obtained
are shown in Table 5. The obtained core film and cladding film had
high refractive index at each measuring wavelength while they
showed no birefringence and thus revealed to be excellent optical
materials.
[0232] Further, the core film and cladding film (both 70 .mu.m
thick) prepared in the same manner as that in Example 8 were
measured for light transmissivity of resin films for optical
materials (having the same composition as that of the core film in
the example, 70 .mu.m thick) using a spectrophotometer (Model
U-3410) manufactured by Hitachi Chemical Co., Limited. As a result,
both the films had 90% or more transmissivity in the visible light
range of 400 to 800 nm, demonstrating that they were resin films
for optical materials having excellent transparency.
TABLE-US-00005 TABLE 5 Refractive index TM TE Polarized Polarized
Wavelength (nm) light light Birefringence Core film 633 1.594 1.594
0.000 830 1.586 1.586 0.000 1300 1.577 1.577 0.000 1550 1.576 1.576
0.000 Cladding 633 1.544 1.546 0.001 film 830 1.537 1.536 0.001
1300 1.530 1.530 0.000 1550 1.529 1.529 0.000
Examples 18 to 27
[0233] The resin compositions of the above-mentioned examples
described in Table 6 were applied to a silicon substrate to
fabricate resin films for optical materials having a thickness of
10 .mu.m and their refractive index and birefringence were measured
(measuring wavelength 830 nm) using a prism-coupler (Model 2020)
manufactured by Metricon Corporation). Further, they were measured
for light transmissivity in the same manner as that in Example 17.
The results obtained are shown in Table 6.
[0234] The resin films for optical materials in Example 18 to 24
showed no birefringence and revealed to be excellent optical
materials having high transparency. Further, the resin films for
optical materials in Examples 25 to 27 were excellent optical
materials, respectively, since they had high refractive index while
they had less birefringence, and still had high transparency.
TABLE-US-00006 TABLE 6 Refractive index Resin TE Polarized TM
Polarized Example Composition light light Birefringence
Transmissivity 18 Example 1 1.583 1.583 0.000 90% or more 19
Example 2 1.565 1.565 0.000 90% or more 20 Example 3 1.506 1.506
0.000 90% or more 21 Example 4 1.537 1.537 0.000 90% or more 22
Example 5 1.529 1.529 0.000 90% or more 23 Example 6 1.532 1.532
0.000 90% or more 24 Example 7 1.573 1.573 0.000 90% or more 25
Example 10 1.613 1.611 0.002 90% or more 26 Example 11 1.607 1.604
0.001 90% or more 27 Example 12 1.604 1.603 0.001 90% or more
INDUSTRIAL APPLICABILITY
[0235] The resin composition for an optical material of the present
invention and the resin films for optical materials that includes
the resin composition of the present invention have excellent
transparency and heat resistance and can be used as, for example,
an optical waveguide, a lens, an optical sealant, an optical
adhesive, a light guide panel, or a diffractive grating. In
particular, they can be advantageously used as a resin film for
optical waveguide. In addition, they can be used as a coating
material, a resist and so on. When they are used as a resin film
for optical waveguides, it is possible to form a thick film having
high transparency, high heat resistance, and high precision.
Therefore, by using the film of the present invention in at least
one of the lower cladding, core, and upper cladding, an optical
waveguide having excellent performance can be obtained. Further,
according to the present invention, a large-area film can be
produced, so optical waveguides can be produced with high
productivity.
* * * * *